Add .squeeze to facet_grid to make it a bit more tolerant

This MR makes frames animations more robust if there are size-1 dimension coordinates which might as well be size-1 non-dimension coordinates.

Can this MR be accepted?

• Implementation ready
• Tests added or adjusted
• Documentation extended or updated

• Code quality
  • Changes follow coding guidelines
  • Checked code coverage on new and adjusted code

• Ready for merging
  • Pipeline passes without warnings
  • History cleaned-up or squash option set
  • Changelog entry added
  • Version number bumped
  • Reviewed & approved by @

Related issues