Upgrade Git for Windows by vendoring in mimalloc v2.2.4 which was released yesterday.

Seeing as the update to v2.2.3 brought a bug that was only revealed after Git for Windows v2.50.0-rc0 made it into Git for Windows' SDK, I do not want to update to v2.2.4 just yet, especially given that the diff between v2.2.3 and v2.2.4 brings more functional changes than just the fix for aforementioned bug.

After Git for Windows v2.50.0 is released (plus a grace period of 1-2 weeks or so in case of a hot-fix release), I would like to upgrade to mimalloc v2.2.4, and while at it, also start monitoring https://github.com/microsoft/mimalloc/tags in the component-updates.yml workflow.