MAINT: Update Python version support

[tturocy]

Python 3.9 has reached end-of-life and Python 3.14 is out.

master (and by implication version 16.5) should be updated to reflect this.

It might also be worth a look to see whether there any areas where we were restricted in using syntax. The one that comes to mind for me is that we shouldn't have to do typing.Union anymore (without having to do a __future__ import).

[tturocy]

I've set up a branch which does the basic Python bumping:

To-dos: @rahulsavani @edwardchalstrey1

• Check documentation reflects the new supported versions
• Check for Python modernisations. The two I can think of are (a) using | in type annotations; (b) always use strict= parameter for zip().

[edwardchalstrey1]

I've set up a branch which does the basic Python bumping:

To-dos: @rahulsavani @edwardchalstrey1

• Check documentation reflects the new supported versions[x] Check for Python modernisations. The two I can think of are (a) using | in type annotations; (b) always use strict= parameter for zip().

@tturocy I opened PR #680 from your branch and added these syntax changes