chore(deps): update dependency pandas to v1.4.0 (#700)

* chore(deps): update dependency pandas to v1.4.0 * add pandas pin for python 3.7 * adjust pin Co-authored-by: Anthonios Partheniou <partheniou@google.com>

Author: renovate-bot

samples/snippets/requirements.txt

@@ -1,4 +1,4 @@
 google-cloud-pubsub==2.9.0
 google-cloud-storage==2.1.0
-pandas==1.3.5; python_version > '3.6'
-pandas==1.1.5; python_version < '3.7'
+pandas==1.3.5; python_version == '3.7'
+pandas==1.4.0; python_version >= '3.8'