chore(deps): update dependency opencensus-ext-flask to v0.7.5 (GoogleCloudPlatform#5831)

Co-authored-by: Dan Lee <[email protected]>

Author: renovate-bot

trace/cloud-trace-demo-app/app/requirements.txt

@@ -3,7 +3,7 @@ google-cloud-trace==0.24.0
 opencensus==0.7.13
 Flask==1.1.4
 opencensus-ext-stackdriver==0.7.4
-opencensus-ext-flask==0.7.4
+opencensus-ext-flask==0.7.5
 opencensus-context==0.1.2
 grpcio==1.37.1
 httpretty==1.1.1