Remove flag content_profiles_errors_metrics

Metric development doesn't need a feature flag, and all the usages
were removed. Now this CL removes the flag declaration.

Bug: 317002318
Bug: 294797589
Test: m -j;
Change-Id: Ic4fe7c2476b22d8262e9536c9abe8272c374e0a0

flags/content_profiles.aconfig

-package: "com.android.bluetooth.flags"
-container: "com.android.btservices"
-
-flag {
-    name: "content_profiles_errors_metrics"
-    namespace: "bluetooth"
-    description: "Enable logging error metrics in content profiles"
-    bug: "317002318"
-}