deps: update dependency com.google.api.grpc:proto-google-iam-v1 to v1…

….2.0 (#645)

pom.xml

@@ -154,7 +154,7 @@
     <gax.version>2.7.1</gax.version>
     <google.api-common.version>2.1.1</google.api-common.version>
     <google.common-protos.version>2.7.0</google.common-protos.version>
-    <google.iam.version>1.1.7</google.iam.version>
+    <google.iam.version>1.2.0</google.iam.version>
     <google.auth.version>1.3.0</google.auth.version>
     <google.api.version>1.32.2</google.api.version>
     <google.http.version>1.40.1</google.http.version>