Help: MSVC_DEBUG_INFORMATION_FORMAT is initialized from associated variable

The `CMAKE_MSVC_DEBUG_INFORMATION_FORMAT` variable docs mention that it
initializes the `MSVC_DEBUG_INFORMATION_FORMAT` target property, but the
property's docs was missing any mention of the variable.

Follow the pattern from commit c1b07ca9da (Help: MSVC_RUNTIME_LIBRARY is
initialized from associated variable, 2022-08-13, v3.25.0-rc1~317^2).

Fixes: #25216