chore: Bump java auth library for Bazel Builds (googleapis#2341)

* deps: Bump Google Java Auth Library to v1.21.0

* chore: Bump Java Auth Library version v1.21.0 for bazel builds

gax-java/dependencies.properties

@@ -37,8 +37,8 @@ version.io_grpc=1.60.0
 #   2) Replace all characters which are neither alphabetic nor digits with the underscore ('_') character
 maven.com_google_api_grpc_proto_google_common_protos=com.google.api.grpc:proto-google-common-protos:2.29.0
 maven.com_google_api_grpc_grpc_google_common_protos=com.google.api.grpc:grpc-google-common-protos:2.29.0
-maven.com_google_auth_google_auth_library_oauth2_http=com.google.auth:google-auth-library-oauth2-http:1.20.0
-maven.com_google_auth_google_auth_library_credentials=com.google.auth:google-auth-library-credentials:1.20.0
+maven.com_google_auth_google_auth_library_oauth2_http=com.google.auth:google-auth-library-oauth2-http:1.21.0
+maven.com_google_auth_google_auth_library_credentials=com.google.auth:google-auth-library-credentials:1.21.0
 maven.io_opencensus_opencensus_api=io.opencensus:opencensus-api:0.31.1
 maven.io_opencensus_opencensus_contrib_grpc_metrics=io.opencensus:opencensus-contrib-grpc-metrics:0.31.1
 maven.io_opencensus_opencensus_contrib_http_util=io.opencensus:opencensus-contrib-http-util:0.31.1