Bump error-prone.version from 2.26.1 to 2.28.0

Bumps `error-prone.version` from 2.26.1 to 2.28.0.

Updates `com.google.errorprone:error_prone_core` from 2.26.1 to 2.28.0
- [Release notes](https://github.com/google/error-prone/releases)
- [Commits](google/error-prone@v2.26.1...v2.28.0)

Updates `com.google.errorprone:error_prone_annotations` from 2.26.1 to 2.28.0
- [Release notes](https://github.com/google/error-prone/releases)
- [Commits](google/error-prone@v2.26.1...v2.28.0)

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

pom.xml

@@ -42,7 +42,7 @@
 
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-    <error-prone.version>2.26.1</error-prone.version>
+    <error-prone.version>2.28.0</error-prone.version>
   </properties>
 
   <build>