Bump error_prone_annotations from 2.9.0 to 2.15.0

Bumps [error_prone_annotations](https://github.com/google/error-prone) from 2.9.0 to 2.15.0.
- [Release notes](https://github.com/google/error-prone/releases)
- [Commits](https://github.com/google/error-prone/compare/v2.9.0...v2.15.0)

---
updated-dependencies:
- dependency-name: com.google.errorprone:error_prone_annotations
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

material-color-utilities/build.gradle

@@ -29,5 +29,5 @@ java {
 }
 
 dependencies {
-    implementation 'com.google.errorprone:error_prone_annotations:2.9.0'
+    implementation 'com.google.errorprone:error_prone_annotations:2.15.0'
 }