Use the misc.highlighting_failure warning sub-type for PygmentsBridge.get_lexer()

[b-kamphorst]

Purpose

add warning type to PygmentsBridge.get_lexer

References

Closes #13334

[b-kamphorst]

Hi! This is my first PR to this project. I tried to follow instructions in updating AUTHORS.rst and CHANGES.rst. I hope the PR is acceptable and I'm happy to take any feedback.

Note: I re-used the existing misc.highlighting_failure warning type as it seems appropriate and was already raised in this class.

[AA-Turner]

I tried to follow instructions in updating AUTHORS.rst and CHANGES.rst.

I don't think you've pushed this commit.

[b-kamphorst]

Classic. Thanks for noting, fixed now.

[AA-Turner]

Thanks!