Bump drf-yasg[validation] from 1.21.5 to 1.21.7

Bumps [drf-yasg[validation]](https://github.com/axnsan12/drf-yasg) from 1.21.5 to 1.21.7.
- [Release notes](https://github.com/axnsan12/drf-yasg/releases)
- [Changelog](https://github.com/axnsan12/drf-yasg/blob/master/docs/changelog.rst)
- [Commits](axnsan12/drf-yasg@1.21.5...1.21.7)

---
updated-dependencies:
- dependency-name: drf-yasg[validation]
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

requirements.txt

@@ -19,7 +19,7 @@ django-timezone-field==5.1
 djangorestframework==3.14.0
 djangorestframework-camel-case==1.4.2
 docutils==0.20.1
-drf-yasg[validation]==1.21.5
+drf-yasg[validation]==1.21.7
 firebase-admin==6.2.0
 flower==2.0.0
 gunicorn[gevent]==20.1.0