chore(deps): update dependency google-api-python-client to v1.8.4 [(#3881)](GoogleCloudPlatform/python-docs-samples#3881)

Co-authored-by: Bu Sun Kim <[email protected]>
Co-authored-by: gcf-merge-on-green[bot] <60162190+gcf-merge-on-green[bot]@users.noreply.github.com>

Author: 3 people

samples/api-client/manager/requirements.txt

@@ -1,6 +1,6 @@
 cryptography==2.9.2
 flaky==3.6.1
-google-api-python-client==1.8.3
+google-api-python-client==1.8.4
 google-auth-httplib2==0.0.3
 google-auth==1.15.0
 google-cloud-iot==1.0.0