Do not keep runtime invisible annotations in proguard.flags

This updates the corresponding Android.bp file to keep the runtime invisible annotations, meaning this should be a no-op.

When RELEASE_R8_ONLY_RUNTIME_VISIBLE_ANNOTATIONS is enabled, keep_runtime_invisible_annotations will become a no-op, which should lead to all runtime invisible annotations being stripped from this build.

Bug: 387958004
Change-Id: Ib0090cd30d44630a1b0a1d1f0605edb7fef8c5cf
Test: existing
diff --git a/Android.bp b/Android.bp
index fd0ed55..05fd866 100644
--- a/Android.bp
+++ b/Android.bp
@@ -32,6 +32,7 @@
     soong_config_variables: {
         build_variant_eng: {
             optimize: {
+                keep_runtime_invisible_annotations: true,
                 proguard_flags_files: [
                     "proguard.flags",
                     "proguard-test.flags",
@@ -39,6 +40,7 @@
             },
             conditions_default: {
                 optimize: {
+                    keep_runtime_invisible_annotations: true,
                     proguard_flags_files: [
                         "proguard.flags",
                         "proguard-release.flags",