remove some redundant using (#5262)

Author: SimonCropp

src/includes/configuration/auto-session-tracking/dotnet.mdx

@@ -7,15 +7,11 @@ We mark the session as:
 To enable sending sessions, set the `AutoSessionTracking` flag to `true`. When enabled, the .NET SDK is creating a session on application startup and ending it on shut down. 
 
 ```csharp {tabTitle:C#}
-using Sentry;
-
 // Add this to the SDK initialization callback
 options.AutoSessionTracking = true; // default: false
 ```
 
 ```fsharp {tabTitle:F#}
-open Sentry
-
 // Add this to the SDK initialization callback
 options.AutoSessionTracking <- true // default: false
 ```

src/includes/configuration/auto-session-tracking/unity.mdx

@@ -3,9 +3,6 @@
 Sentry SDK subscribes to `OnApplicationPause` and `OnApplicationFocus` events to track if the application has focus or if it has been put in the background. On resume within `AutoSessionTrackingInterval` the session will be continued. The default value is `30 seconds`. Otherwise, the previous session will be ended and we create a new one.
 
 ```csharp {tabTitle:C#}
-using System;
-using Sentry;
-
 // Add this to the SDK initialization callback
 options.AutoSessionTrackingInterval = TimeSpan.FromSeconds(30);
 ```

src/includes/performance/automatic-instrumentation-integrations/dotnet.mdx

@@ -9,17 +9,13 @@ Starting with version 3.9.0, the SDK automatically integrates with Entity Framew
 If you don't want to have this integration, you can disable it on `SentryOptions` by calling `DisableDiagnosticSourceIntegration();`
 
 ```csharp
-using Sentry;
-
 option.DisableDiagnosticSourceIntegration();
 ```
 
 If your project doesn't match any of the conditions above, (for example, it targets .NET Framework 4.6.1 and uses only the `Sentry` package), you can still manually activate those instrumentations by including the package `Sentry.DiagnosticSource` and enabling it during on the SDK's initialization.
 
 ```csharp
 // Requires NuGet package: Sentry.DiagnosticSource
-using Sentry;
-
 option.AddDiagnosticSourceIntegration();
 ```
 

src/includes/performance/traces-sample-rate/dotnet.mdx

@@ -1,6 +1,4 @@
 ```csharp
-using Sentry;
-
 // Add this to the SDK initialization callback
 options.TracesSampleRate = 0.2;
 ```

src/includes/set-environment/dotnet.mdx

@@ -1,13 +1,9 @@
 ```csharp
-using Sentry;
-
 // Add this to the SDK initialization callback
 options.Environment = "production";
 ```
 
 ```fsharp
-open Sentry
-
 // Add this to the SDK initialization callback
 options.Environment <- "production"
 ```

src/includes/set-environment/dotnet.nlog.mdx

@@ -29,15 +29,11 @@ For more information on how to dynamically set event data via `NLog.config`, see
 ```
 
 ```csharp
-using Sentry;
-
 // Add this to the SDK initialization callback
 options.Environment = "production";
 ```
 
 ```fsharp
-open Sentry
-
 // Add this to the SDK initialization callback
 options.Environment <- "production"
 ```

src/includes/set-release/dotnet.mdx

@@ -1,13 +1,9 @@
 ```csharp {tabTitle:C#}
-using Sentry;
-
 // Add this to the SDK initialization callback
 options.Release = "my-project-name@2.3.12";
 ```
 
 ```fsharp {tabTitle:F#}
-open Sentry
-
 // Add this to the SDK initialization callback
 options.Release <- "my-project-name@2.3.12"
 ```

src/includes/set-release/dotnet.nlog.mdx

@@ -28,15 +28,11 @@ For more information on how to dynamically set event data via `NLog.config`, see
 ```
 
 ```csharp
-using Sentry;
-
 // Add this to the SDK initialization callback
 options.Release = "my-project-name@2.3.12";
 ```
 
 ```fsharp
-open Sentry
-
 // Add this to the SDK initialization callback
 options.Release <- "my-project-name@2.3.12"
 ```

src/platforms/dotnet/common/configuration/disable-integrations.mdx

@@ -9,15 +9,11 @@ All of Sentry’s SDKs provide integrations, which extend functionality of the S
 To disable an integration, for example, the automatic capture of unhandled exceptions:
 
 ```csharp
-using Sentry;
-
 // Add it to your Sentry SDK initialization block:
 options.DisableAppDomainUnhandledExceptionCapture()
 ```
 
 ```fsharp
-open Sentry
-
 // Add it to your Sentry SDK initialization block:
 options.DisableAppDomainUnhandledExceptionCapture()
 ```

src/platforms/dotnet/guides/aspnetcore/builtin-sampling-context.mdx

@@ -8,8 +8,6 @@ You can sample transactions by providing a delegate that makes a decision based
 For example, here's how to sample a transaction based on the requested path:
 
 ```csharp
-using Sentry;
-
 // Add this to the SDK initialization callback
 options.TracesSampler = context =>
 {