Bump tensorflow from 2.1.2 to 2.6.4

Bumps [tensorflow](https://github.com/tensorflow/tensorflow) from 2.1.2 to 2.6.4.
- [Release notes](https://github.com/tensorflow/tensorflow/releases)
- [Changelog](https://github.com/tensorflow/tensorflow/blob/master/RELEASE.md)
- [Commits](tensorflow/tensorflow@v2.1.2...v2.6.4)

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

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Author: dependabot[bot]

requirements-python-3.7.4.txt

@@ -39,7 +39,7 @@ ruamel-yaml==0.15.46
 scipy==1.4.1
 six==1.14.0
 tensorboard==2.1.0
-tensorflow==2.1.2
+tensorflow==2.6.4
 tensorflow-estimator==2.1.0
 tensornets==0.4.3
 termcolor==1.1.0

requirements.txt

@@ -29,7 +29,7 @@ rsa==4.0
 scipy==1.4.1
 six==1.14.0
 tensorboard==2.1.0
-tensorflow==2.1.2
+tensorflow==2.6.4
 tensorflow-estimator==2.1.0
 tensornets==0.4.3
 termcolor==1.1.0