Update mbed-tools requirement in /scripts/local-requirements (#412)

Updates the requirements on [mbed-tools](https://github.com/ARMmbed/mbed-tools) to permit the latest version.
- [Release notes](https://github.com/ARMmbed/mbed-tools/releases)
- [Changelog](https://github.com/ARMmbed/mbed-tools/blob/master/CHANGELOG.md)
- [Commits](ARMmbed/mbed-tools@7.3.3...7.50.0)

---
updated-dependencies:
- dependency-name: mbed-tools
  dependency-type: direct:production
...

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scripts/local-requirements/requirements.txt

@@ -1,4 +1,4 @@
 PyYAML~=5.1
-mbed-tools~=7.3.3
+mbed-tools~=7.50.0
 cantools~=36.2
 matplotlib~=3.4