Bump fonttools in /mpcontribs-serverless/dependencies

Bumps [fonttools](https://github.com/fonttools/fonttools) from 4.38.0 to 4.43.0.
- [Release notes](https://github.com/fonttools/fonttools/releases)
- [Changelog](https://github.com/fonttools/fonttools/blob/main/NEWS.rst)
- [Commits](fonttools/fonttools@4.38.0...4.43.0)

---
updated-dependencies:
- dependency-name: fonttools
  dependency-type: indirect
...

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

mpcontribs-serverless/dependencies/requirements.txt

@@ -55,7 +55,7 @@ filetype==1.1.0
     # via mpcontribs-client
 flatten-dict==0.4.2
     # via mpcontribs-client
-fonttools==4.38.0
+fonttools==4.43.0
     # via matplotlib
 future==0.18.3
     # via uncertainties