Remove -prerelease for MSVC 2022

[bdbaddog]

Remove prerelease flag for MSVC 2022 in prep for SCons 4.3 release and MSVC 2022 release.

Contributor Checklist:

• I have created a new test or updated the unit tests to cover the new/changed functionality.
• I have updated CHANGES.txt (and read the README.rst)
• I have updated the appropriate documentation

[LeonarddeR]

Is there anything against supporting building with preview versions of Visual Studio on request? VS2022 has just been released but the first minor update has landed in the preview channel. If I understand this pr correctly, it removes support for preview versions.

[mwichmann]

That support will appear as part of a different change, to address #4048. The maintainer wanted to split the topics.

[bdbaddog]

Is there anything against supporting building with preview versions of Visual Studio on request? VS2022 has just been released but the first minor update has landed in the preview channel. If I understand this pr correctly, it removes support for preview versions.

There was never a released version of SCons with support for pre-release MSVC.
The implementation in question isn't one we'd like to release.
So that logic is being removed.
We'll release SCons today/tomorrow with 2022 support and then figure out a comprehensive (and SCons'ian) way to support prerelease going forward. Hopefully soon.

As @mwichmann said any further discussion should happen in #4048