Fix gRPC to call credentials.before_request (#116)

diff --git a/tox.ini b/tox.ini
index 0a98945..a2f7362 100644
--- a/tox.ini
+++ b/tox.ini
@@ -33,7 +33,7 @@
 deps =
   {[testenv]deps}
   nox-automation
-  gapic-google-pubsub-v1==0.11.1
+  gapic-google-cloud-pubsub-v1==0.15.0
 passenv =
   SKIP_APP_ENGINE_SYSTEM_TEST
   CLOUD_SDK_ROOT
@@ -46,7 +46,7 @@
 deps =
   {[testenv]deps}
   nox-automation
-  gapic-google-pubsub-v1==0.11.1
+  gapic-google-cloud-pubsub-v1==0.15.0
 passenv =
   SKIP_APP_ENGINE_SYSTEM_TEST
   CLOUD_SDK_ROOT