chore(deps): update dependency six to v1.15.0 [(#3853)](GoogleCloudPlatform/python-docs-samples#3853)

Author: renovate-bot

packages/google-cloud-python-speech/samples/microphone/requirements.txt

@@ -1,4 +1,4 @@
 google-cloud-speech==1.3.2
 pyaudio==0.2.11
-six==1.14.0
+six==1.15.0