chore(deps): update dependency starlette to v0.27.0 [security]

Author: renovate[bot]

docs/requirements.txt

@@ -40,7 +40,7 @@ redis==4.3.6
 regex==2020.2.20
 requests==2.23.0
 six==1.14.0
-starlette==0.25.0
+starlette==0.27.0
 toml==0.10.0
 tornado==6.0.4
 tqdm==4.50.0; python_version > "2.7"