Avoid a dependency on javax.annotation.Generated

java.annotations.common isn't provided by default in JDK 9, see
https://bugs.openjdk.java.net/browse/JDK-8152842

This helps with #448

RELNOTES: N/A

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=155635468

check_api/src/main/java/com/google/errorprone/SuppressionHelper.java

@@ -30,7 +30,6 @@
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.Set;
-import javax.annotation.Generated;
 
 /**
  * Encapsulates the logic of handling suppressions, both via {@code @SuppressWarnings} and via
@@ -105,7 +104,7 @@ public SuppressionInfo extendSuppressionSets(
       VisitorState state) {
 
     boolean newInGeneratedCode =
-        inGeneratedCode || ASTHelpers.hasAnnotation(sym, Generated.class, state);
+        inGeneratedCode || ASTHelpers.hasAnnotation(sym, "javax.annotation.Generated", state);
 
     /**
      * Handle custom suppression annotations.