Bump starlette in /{{cookiecutter.project_slug}}/backend (#88)

Bumps [starlette](https://github.com/encode/starlette) from 0.13.4 to 0.13.6.
- [Release notes](https://github.com/encode/starlette/releases)
- [Changelog](https://github.com/encode/starlette/blob/master/docs/release-notes.md)
- [Commits](Kludex/starlette@0.13.4...0.13.6)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]

{{cookiecutter.project_slug}}/backend/requirements.txt

@@ -11,7 +11,7 @@ psycopg2==2.8.5
 pytest==5.4.3
 requests==2.24.0
 SQLAlchemy==1.3.18
-starlette==0.13.4
+starlette==0.13.6
 uvicorn==0.11.6
 passlib==1.7.2
 bcrypt==3.1.7