Bump webargs from 2.1.0 to 5.1.3

Bumps [webargs](https://github.com/marshmallow-code/webargs) from 2.1.0 to 5.1.3.
- [Release notes](https://github.com/marshmallow-code/webargs/releases)
- [Changelog](https://github.com/marshmallow-code/webargs/blob/dev/CHANGELOG.rst)
- [Commits](marshmallow-code/webargs@2.1.0...5.1.3)

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

Author: dependabot[bot]

requirements.txt

@@ -128,5 +128,5 @@ six==1.11.0
 SQLAlchemy==1.1.5
 SQLAlchemy-Utils==0.32.12
 urllib3==1.22
-webargs==2.1.0
+webargs==5.1.3
 Werkzeug==0.15.3