net-imap: Update 0.4.24->0.6.4.1

[Sharpie]

Short description

This commit upgrades the bundled net-imap gem in Ruby 3.2.11 from the previous patched version of 0.4.24 to 0.6.4.1. This release contains fixes for the following medium and low-severity security issues:

• GHSA-46q3-7gv7-qmgg
• GHSA-8p34-64r3-mwg8
• GHSA-c4fp-cxrr-mj66

There will be no further upstream releases to Ruby 3.2, thus we have to upgrade this gem ourselves. The 0.5.0 and 0.6.0 releases have some breaking changes, however the net-imap gem was completely broken in OpenVox 8 for quite a few release without any issue reports -- which suggests low usage.

The 0.6 release series was selected as support has ended for the 0.4 line and this syncs OpenVox 8 behavior with Ruby 4 in OpenVox 9.

Checklist

I have:

• read the CONTRIBUTING.md document
• read and accepted the Developer Certificate of Origin document and added a Signed-off-by annotation to each of my commits
• read and accepted the AI Policy document and added Generated-by or Assisted-by annotations to each of my commits created with the help of an AI agent
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)