fix(apple): Usages of sendDefaultPii (#12833)

Document the only usage of sendDefaultPii in the Cocoa SDK.

Fixes GH-12751

Author: philipphofmann

docs/platforms/apple/common/data-management/data-collected.mdx

@@ -12,6 +12,11 @@ The category types and amount of data collected vary, depending on the integrati
 
 The <PlatformLink to="/configuration/http-client-errors">HTTP Client Errors</PlatformLink>, which are enabled by default, send the HTTP headers of the failed request and response to Sentry. The SDK uses a [denylist](https://github.com/getsentry/sentry-cocoa/blob/main/Sources/Swift/Tools/HTTPHeaderSanitizer.swift) to filter out any headers that contain sensitive data.
 
+## Users' IP Addresses
+
+By default, the Sentry SDK doesn't send the user's IP address. Once enabled, the Sentry backend services will infer the user ip address based on the incoming request, unless certain integrations you can enable override this behavior.
+
+To enable sending the user's IP address, set <PlatformLink to="/configuration/options/#send-default-pii">`sendDefaultPii=true`</PlatformLink>.
 
 ## Request URL