Remove Octave/MATLAB example test_curl.m

[Tony-Drummond]

Describe the bug
The octave script: test_curl.m, uses the Octave/MATLAB function curl to compute:
curl = div2D(k, m, dx, n, dy)*F;
where F is defined in the article: https://doi.org/10.1016/j.cam.2019.06.042

This example does not work with MOLE's curl2D implementations, and it would be best to remove it from the MOLE core repository of examples.

In the future, we will start a list of MOLE functions that will be deprecated, with pointers to the new functionality. However, this example needs to be simply removed.

Additional context
In the future, we will start a list of MOLE functions that will be deprecated, with pointers to the new functionality. However, this example needs to be simply removed.

Keep-open request

• I am requesting maintainer review for keep-open.

Reason:
This issue will be closed by removing this file from the list of Octave/MATLAB examples.