Bump tensorflow from 1.14 to 2.3.1

Bumps [tensorflow](https://github.com/tensorflow/tensorflow) from 1.14 to 2.3.1.
- [Release notes](https://github.com/tensorflow/tensorflow/releases)
- [Changelog](https://github.com/tensorflow/tensorflow/blob/master/RELEASE.md)
- [Commits](tensorflow/tensorflow@v1.14.0...v2.3.1)

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

Author: dependabot[bot]

docs/requirements.txt

@@ -8,7 +8,7 @@ matplotlib
 numpy>=1.16
 pandas
 scipy>=0.17
-tensorflow==1.14
+tensorflow==2.3.1
 xport
 scikit-image
 requests

setup.py

@@ -24,7 +24,7 @@
             'cvxpy',
             'cvxopt',
             'Image',
-            'tensorflow==1.14',
+            'tensorflow==2.3.1',
 	    'h5py<3.0.0',
             'keras==2.3.1',
             'matplotlib',