Bump GAX dependency to 0.15.14. (#3752)

Author: lukesneeringer

packages/google-cloud-videointelligence/setup.py

@@ -43,7 +43,7 @@
     packages=find_packages(exclude=('tests*',)),
     install_requires=(
         'googleapis-common-protos >= 1.5.2, < 2.0dev',
-        'google-gax >= 0.15.12, < 0.16dev',
+        'google-gax >= 0.15.14, < 0.16dev',
         'six >= 1.10.0',
     ),
     url='https://github.com/GoogleCloudPlatform/google-cloud-python',