chore(deps): update dependency google-api-python-client to v2.20.0 (#1519)

diff --git a/samples/compute/requirements.txt b/samples/compute/requirements.txt
index 094c8e5..8d52d8b 100644
--- a/samples/compute/requirements.txt
+++ b/samples/compute/requirements.txt
@@ -1,3 +1,3 @@
-google-api-python-client==2.19.1
+google-api-python-client==2.20.0
 google-auth==2.0.2
 google-auth-httplib2==0.1.0