Remove double-backslashes from latex labels passed to matplotlib.

[AlexandreGoettel]

Addresses #836
As far as I can tell, the issue is due to a bug in bilby_pipe, but I noticed that there is already a function to remove matplotlib errors in bilby/core/result.py.

This PR simply adds a line to this function to convert "\" into "".

Either way I think this is a good thing to have, as I can't think of a scenario where having "\" in a matplotlib latex string is a good idea.

[mj-will]

Have you checked to see how this interacts with raw strings (e.g. r"$\mathcal{M}$")?

[AlexandreGoettel]

Have you checked to see how this interacts with raw strings (e.g. r"$\mathcal{M}$")?

Not 100% what you mean but afaik a variable defined as a raw string just becomes a string (with different creation rules) i.e.:
r"$\mathcal{M}$" == "$\\mathcal{M}$" will return True. The code above will work in both cases.

[mj-will]

Not 100% what you mean but afaik a variable defined as a raw string just becomes a string (with different creation rules) i.e.: r"$\mathcal{M}$" == "$\\mathcal{M}$" will return True. The code above will work in both cases.

Ah, I didn't know that, makes sense then :)