Update bundled Tcl/Tk to 8.6.15 (Windows, macOS installer)

[zware]

Proposal:

8.6.15 was released on Sep 13, 2024

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-124448: Update Windows builds to use Tcl/Tk 8.6.15 #124449
• gh-124448: Update bundled Tcl/Tk in macOS installer to 8.6.15. #124453
• [3.13] gh-124448: Update Windows builds to use Tcl/Tk 8.6.15 #125795
• [3.12] gh-124448: Update Windows builds to use Tcl/Tk 8.6.15 #125796
• [3.12] gh-124448: Update bundled Tcl/Tk in macOS installer to 8.6.15. (GH-124453) #125800
• [3.13] gh-124448: Update bundled Tcl/Tk in macOS installer to 8.6.15. (GH-124453) #125801

[zware]

See also gh-124111.