Fix example notebook

[AGaliciaMartinez]

This PR fixed a few issues with the latest tensorflow release.

• Tensorflow changed the numpy experimental option needed for autocasting. Now a new argument is needed to make it work.
• Added a test to catch changes in autocasting.
• Fixed version of tensorflow to avoid any future conflicts.
• Fixed an issue with the optimizer. It no longer has a minimize argument.
• Fixed test and docs pipeline. It was installing qutip from dev major.

[AGaliciaMartinez]

To take a look at the example go to: https://github.com/AGaliciaMartinez/qutip-tensorflow/blob/fix_example_notebook/examples/rotation_optimization.ipynb. You can open the example in colab.

[AGaliciaMartinez]

Fixed the issue with he docs.

[coveralls]

Pull Request Test Coverage Report for Build 8549975871

Warning: This coverage report may be inaccurate.

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Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 97.12%

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Totals
Change from base Build 4495170632:	0.0%
Covered Lines:	371
Relevant Lines:	382

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💛 - Coveralls