Bump tensorflow from 2.1.2 to 2.4.0 in /ModelTrainer
Bump tensorflow from 2.1.2 to 2.4.0 in /ModelTrainer

Bumps [tensorflow](https://github.com/tensorflow/tensorflow) from 2.1.2 to 2.4.0.
- [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/v2.1.2...v2.4.0)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
apacha/MusicSymbolClassifier