Bump error_prone_core to 2.2.0

Change-Id: I22157643740a103bbc6b12a49784f8bf2eee6bef

pom.xml

diff --git a/pom.xml b/pom.xml
index 78aaf8b..dc91f3a 100644
--- a/pom.xml
+++ b/pom.xml
@@ -399,7 +399,7 @@
           <dependency>
             <groupId>com.google.errorprone</groupId>
             <artifactId>error_prone_core</artifactId>
-            <version>2.1.1</version>
+            <version>2.2.0</version>
           </dependency>
         </dependencies>
       </plugin>