Update proguard-android-optimize.txt link in r8-optimization.md

Updates the URL for the proguard-android-optimize.txt file to point to the rules_android repository instead of the bazelbuild examples repository.

PiperOrigin-RevId: 970473584
Change-Id: Ia24d96411a1e64b133c7cd57f38ef82169af44a4

docs/r8-optimization.md

diff --git a/docs/r8-optimization.md b/docs/r8-optimization.md
index 094ce3c..bb8f11c 100644
--- a/docs/r8-optimization.md
+++ b/docs/r8-optimization.md
@@ -50,7 +50,7 @@
     files containing keep rules and optimization directives. Specifying this
     attribute enables R8 code shrinking and optimization. Typically, this
     includes:
-*   [`proguard-android-optimize.txt`](https://github.com/bazelbuild/examples/tree/main/android/r8-optimized/proguard-android-optimize.txt):
+*   [`proguard-android-optimize.txt`](https://github.com/bazelbuild/rules_android/blob/main/examples/r8-optimized/proguard-android-optimize.txt):
     Contains standard recommended Android app optimizations and default keep
     rules (equivalent to the default configuration provided by the Android
     Gradle Plugin). You can download it from the example repository and place it