Update mac legacy runner to macos-13

[softins]

Short description of changes

Update the build runner for Mac legacy from macos-12 to macos-13. The version of xcode is left unchanged at 14.2.0, as this is still supported on macos-13.

CHANGELOG: Build: Updated the Github build runner for MacOS Legacy to macos-13

Context: Fixes an issue?

The macos-12 runner has been discontinued by Github, as mentioned in #3433. This PR fixes the MacOS Legacy build.

Does this change need documentation? What needs to be documented and how?

Not really.

Status of this Pull Request

Tested and working. I've installed the image built with this change and it appears to work fine.

What is missing until this pull request can be merged?

Nothing

Checklist

• I've verified that this Pull Request follows the general code principles
• I tested my code and it does what I want
• My code follows the style guide
• I waited some time after this Pull Request was opened and all GitHub checks completed without errors. (except iOS)
• I've filled all the content above

[ann0see]

Legacy also works on macOS 15.1.1

[pljones]

Can't say whether this is right in any way other than it changes "12" to "13" in two places.