chore(deps): update dependency ipython to v7.15.0 [(#3917)](GoogleCloudPlatform/python-docs-samples#3917)

Co-authored-by: Takashi Matsuo <[email protected]>

Author: 2 people

samples/snippets/requirements.txt

@@ -1,5 +1,5 @@
 google-cloud-bigquery[pandas]==1.24.0
 google-auth-oauthlib==0.4.1
-ipython==7.14.0
+ipython==7.15.0
 matplotlib==3.2.1
 pytz==2020.1