manual §6.6: copy-paste error

[umlaeute]

there's a copy-paste error in §6.6 of the manual, where it reads

<p>Then install to the default location (C:32 or C:64) and follow the setup/update info on the Msys2 webpage.</p>

this was introduced when converting the INSTALL.txt to html by @Lucarda in 1c44e3ef.

however the original INSTALL.txt reads:

Then install to the default location (C:\msys32 or C:\msys64) and follow the

[umlaeute]

@porres i've pushed a fix directly to your doc-updates branch

[porres]

seems something broke in the compile tests

[umlaeute]

afaict this is unrelated to the PR (instead, there's a general problem with setting up one of the build environments; it's been a bit unstable for a while, and I think I will just allow this specific environment to fail)