Bump flask-talisman from 0.5.1 to 0.6.0

Bumps [flask-talisman](https://github.com/GoogleCloudPlatform/flask-talisman) from 0.5.1 to 0.6.0.
- [Release notes](https://github.com/GoogleCloudPlatform/flask-talisman/releases)
- [Commits](GoogleCloudPlatform/flask-talisman@v0.5.1...v0.6.0)

Signed-off-by: dependabot[bot] <support@dependabot.com>

requirements.txt

@@ -7,7 +7,7 @@ Flask==1.0.2
 Flask-SSLify==0.1.5
 Flask-Testing==0.7.1
 Flask-SeaSurf==0.2.2
-flask-talisman==0.5.1
+flask-talisman==0.6.0
 gunicorn==19.9.0
 pycodestyle==2.4.0
 pydocstyle==2.1.1