Make download_from_google_storage print less during runhooks.

Add the --quiet flag to the download_from_google_storage runhooks
step to prevent it from spamming the console when all the files
are already downloaded.

NOTRY=True

Review URL: https://codereview.webrtc.org/1527713003

Cr-Commit-Position: refs/heads/master@{#11090}
diff --git a/DEPS b/DEPS
index 9ea6c8d..724915e 100644
--- a/DEPS
+++ b/DEPS
@@ -102,6 +102,7 @@
                '--recursive',
                '--num_threads=10',
                '--no_auth',
+               '--quiet',
                '--bucket', 'chromium-webrtc-resources',
                'src/resources'],
   },