deps: update dependency com.google.errorprone:error_prone_annotations to v2.9.0 (#266)

Author: renovate-bot

build.gradle

@@ -47,7 +47,7 @@ ext {
       auto_value_annotations: 'com.google.auto.value:auto-value-annotations:1.8.2',
       guava: 'com.google.guava:guava:30.1.1-jre',
       jsr305: 'com.google.code.findbugs:jsr305:3.0.2',
-      error_prone_annotations: 'com.google.errorprone:error_prone_annotations:2.8.1',
+      error_prone_annotations: 'com.google.errorprone:error_prone_annotations:2.9.0',
 
       // Testing
       junit: 'junit:junit:4.13.2',