deps: update dependency com.google.api:gax-bom to v2.21.0 (#1070)

* deps: update dependency com.google.api:gax-bom to v2.21.0

* deps: Updating proto-google-common-protos to 2.12.0

Co-authored-by: Deepankar Dixit <[email protected]>

Author: renovate-bot

pom.xml

@@ -151,7 +151,7 @@
     <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
     <github.global.server>github</github.global.server>
     <site.installationModule>google-cloud-core-parent</site.installationModule>
-    <gax.version>2.20.1</gax.version>
+    <gax.version>2.21.0</gax.version>
     <google.api-common.version>2.4.0</google.api-common.version>
     <google.common-protos.version>2.12.0</google.common-protos.version>
     <google.iam.version>1.7.0</google.iam.version>