Bump tensorflow from 2.7.0 to 2.8.0 in /cvat/requirements (#4311)

Bumps [tensorflow](https://github.com/tensorflow/tensorflow) from 2.7.0 to 2.8.0.
- [Release notes](https://github.com/tensorflow/tensorflow/releases)
- [Changelog](https://github.com/tensorflow/tensorflow/blob/master/RELEASE.md)
- [Commits](https://github.com/tensorflow/tensorflow/compare/v2.7.0...v2.8.0)

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

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cvat/requirements/base.txt

@@ -37,7 +37,7 @@ h5py==2.10.0
 django-cors-headers==3.5.0
 furl==2.1.0
 av==8.0.2 --no-binary=av
-tensorflow==2.7.0 # Optional requirement of Datumaro
+tensorflow==2.8.0 # Optional requirement of Datumaro
 # The package is used by pyunpack as a command line tool to support multiple
 # archives. Don't use as a python module because it has GPL license.
 patool==1.12