Bump sanic from 19.6.3 to 20.12.7 in /feature_engine

Bumps [sanic](https://github.com/sanic-org/sanic) from 19.6.3 to 20.12.7.
- [Release notes](https://github.com/sanic-org/sanic/releases)
- [Commits](sanic-org/sanic@v19.6.3...v20.12.7)

---
updated-dependencies:
- dependency-name: sanic
  dependency-type: direct:production
...

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

feature_engine/requirements.txt

@@ -136,7 +136,7 @@ rsa==4.0
 ruamel.yaml==0.16.7
 Rx==1.6.3
 safetensors==0.4.2
-sanic==19.6.3
+sanic==20.12.7
 sanic-compress==0.1.1
 Sanic-Cors==0.9.9.post4
 Sanic-GraphQL==1.1.0