cmake: drop VS2010 "Dialog Hell" workaround added in 2013

cmake: drop VS2010 "Dialog Hell" workaround added in 2013

Delete the workaround added via a94a68a3c1d04ccb53e46baa69753bbf6354ee14
(2013-02-04). The commit message has no details. The comment mentions
"Dialog Hell", and seems to fix CMake missing to regenerate `CURL.sln`
with VS2010. It also added a FIXME saying the workaround can be deleted
with future versions of CMake.

At the time CMake's latest version was v2.8.10.

curl now requires v3.7 (2018) minimum, and v3.24 (2022) was the
latest CMake natively supporting VS2010. Assume this has since been
fixed.

Also: format an MSVC version reference in comment.

Closes #15973