Update Jetpack version for WordPress 6.7 and newer to 15.0

[rinatkhaziev]

Description

This pull request updates the default Jetpack version for WordPress 6.7 and newer. The change ensures that new sites running the latest WordPress will use the most recent Jetpack release.

Version update:

• Updated the return value in the vip_default_jetpack_version() function in jetpack.php so that WordPress 6.7 and newer will now default to Jetpack version 15.0 instead of 14.9.

Changelog Description

Updated

• Default Jetpack version to 15.0

Pre-review checklist

Please make sure the items below have been covered before requesting a review:

• This change works and has been tested locally or in Codespaces (or has an appropriate fallback).
• This change works and has been tested on a sandbox.
• This change has relevant unit tests (if applicable).
• This change uses a rollout method to ease with deployment (if applicable - especially for large scale actions that require writes).
• This change has relevant documentation additions / updates (if applicable).
• I've created a changelog description that aligns with the provided examples.

Pre-deploy checklist

• VIP staff: Ensure any alerts added/updated conform to internal standards (see internal documentation).

Steps to Test

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 33.61%. Comparing base (57c86e4) to head (ab290e5).

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #6515   +/-   ##
==========================================
  Coverage      33.61%   33.61%           
  Complexity      4991     4991           
==========================================
  Files            292      292           
  Lines          21082    21082           
==========================================
  Hits            7086     7086           
  Misses         13996    13996           

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