Update Swashbuckle.AspNetCore package version to 5.6.3 (#26391)

Fixes #26301

As part of 5.0-preview8, we added Swashbuckle to ASP.NET Core's API project templates. Swashbuckle's developer
team has been active of late and has issued a new minor version that has enhancements and bug fixes. We'd like
to pick this up.

Users currently see a package update prompt on a brand new template. Missing useful bug fixes with the current version.

No

Low. This a minor version update that is recommended by Swashbuckle. I verified the update locally, our tests verify that the template builds and is usable with this change.
We have CTI coverage for end-to-end scenarios with Swashbuckle.

Author: pranavkm

eng/Versions.props

@@ -243,7 +243,7 @@
     <SerilogSinksFilePackageVersion>4.0.0</SerilogSinksFilePackageVersion>
     <StackExchangeRedisPackageVersion>2.0.593</StackExchangeRedisPackageVersion>
     <SystemReactiveLinqPackageVersion>3.1.1</SystemReactiveLinqPackageVersion>
-    <SwashbuckleAspNetCorePackageVersion>5.5.1</SwashbuckleAspNetCorePackageVersion>
+    <SwashbuckleAspNetCorePackageVersion>5.6.3</SwashbuckleAspNetCorePackageVersion>
     <XunitAbstractionsPackageVersion>2.0.3</XunitAbstractionsPackageVersion>
     <XunitAnalyzersPackageVersion>0.10.0</XunitAnalyzersPackageVersion>
     <XunitVersion>2.4.1</XunitVersion>