Update dependency com.google.errorprone:error_prone_annotations to v2…

….31.0

build.gradle

@@ -21,7 +21,7 @@ repositories {
   maven { url 'https://oss.sonatype.org/content/repositories/snapshots/' }
 }
 
-ext.errorproneVersion = '2.30.0'
+ext.errorproneVersion = '2.31.0'
 
 dependencies {
   // ical4j version 4 deprecates its own date representation and uses java.time.* instead.  This