Add Python 3.14 to the testing

[cclauss]

Describe the changes you have made:

Add Python 3.14 to the testing.

• https://www.python.org/downloads/release/python-3140/

-        python-version: ["3.10", "3.12"]
+        python-version: ["3.10", "3.12", "3.14"]

Reference any relevant issues (e.g. "Fixes #000"):

Pre-Submission Checklist (optional but appreciated):

• I have included relevant documentation updates (stored in /docs)
• I have read docs/CONTRIBUTING.md
• I have read docs/ROADMAP.md

OS Tests (optional but appreciated):

• Tested on Windows
• Tested on MacOS
• Tested on Linux

@Notnaton

[endolith]

This was limited in #1637. Did you change something so that it works now? (actions/setup-python@v6?)

[cclauss]

There was no explanation of why the upper limit was set in that PR, but it was created before Py3.14 was released.

[endolith]

From a Discord comment:

It needs to be 3.10 or 3.11 because of tiktoken not working with 3.12+

[cclauss]

Perhaps there should be a pytest to cover tiktoken because tests have been passing on Py3.12.

Does CI fail on Py3.14?

[cclauss]

https://github.com/openai/tiktoken/blob/main/CHANGELOG.md supports Py3.14.