deps: update google.core.version to v2.8.21

Author: renovate-bot

Diff for: first-party-dependencies/pom.xml

@@ -63,7 +63,7 @@
     <protobuf.version>3.21.7</protobuf.version>
     <google.api-common.version>2.2.1</google.api-common.version>
     <google.common-protos.version>2.9.6</google.common-protos.version>
-    <google.core.version>2.8.20</google.core.version>
+    <google.core.version>2.8.21</google.core.version>
     <google.auth.version>1.12.0</google.auth.version>
     <google.http-client.version>1.42.2</google.http-client.version>
     <google.oauth-client.version>1.34.1</google.oauth-client.version>