fix(distribution): Update ProGuard rules for new DistributionIntegration class path

- Update ProGuard rules from `internal.DistributionIntegration` to `DistributionIntegration`
- Fixes R8 missing class error in release builds
- Ensures DistributionIntegration class is properly kept during code shrinking

This addresses the build failure in Android integration tests where R8 was
removing the DistributionIntegration class that is referenced by AndroidOptionsInitializer.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: runningcode

sentry-android-core/proguard-rules.pro

@@ -80,6 +80,6 @@
 ##---------------End: proguard configuration for sentry-android-replay  ----------
 
 ##---------------Begin: proguard configuration for sentry-android-distribution  ----------
--dontwarn io.sentry.android.distribution.internal.DistributionIntegration
--keepnames class io.sentry.android.distribution.internal.DistributionIntegration
+-dontwarn io.sentry.android.distribution.DistributionIntegration
+-keepnames class io.sentry.android.distribution.DistributionIntegration
 ##---------------End: proguard configuration for sentry-android-distribution  ----------