julia: Update to version 1.12.6, fix checkver

[Heptazhou]

FWIW, another source could be juliaup/versiondb.json, but julialang.org/config.md is totally good enough.

Ref: ScoopInstaller/Versions#2922.

• Use conventional PR title: <manifest-name[@version]|chore>: <general summary of the pull request>
• I have read the Contributing Guide

[coderabbitai]

Walkthrough

This PR updates the Julia package manifest in the Scoop installer from version 1.12.2 to 1.12.6. The update includes changes to package metadata, Windows binary download URLs and checksums, and the configuration for detecting stable Julia releases from the upstream repository.

Changes

Julia 1.12.6 Manifest Update

Layer / File(s)	Summary
Metadata and description updates bucket/julia.json	Version, description, homepage, and notes fields are updated to 1.12.6; notes now mention juliaup for managing multiple Julia versions.
Binary downloads and checksums bucket/julia.json	Windows 64bit and 32bit archive URLs are updated to 1.12.6 releases; corresponding SHA256 hashes and extract directory (julia-1.12.6) are provided for both platforms.
Version detection configuration bucket/julia.json	The checkver URL source changed from julialang downloads page to JuliaLang's config.md in www.julialang.org repository; the regex pattern now extracts the stable_release field instead of the prior text format.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description check	✅ Passed	The PR description includes both required checklist items marked as complete, though it lacks detail about the specific changes made to the manifest file.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title directly summarizes the main changes: updating Julia to version 1.12.6 and fixing the checkver mechanism, which aligns with the primary objectives.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

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[z-Fng]

/verify

[github-actions]

All changes look good.

Wait for review from human collaborators.

julia

• Lint
• Description
• License
• Hashes
• Checkver
• Autoupdate
• Autoupdate Hash Extraction

Check the full log for details.

[z-Fng]

Thank you for your contribution!