[mp3lame] Fix lib suffix on Unix

[NancyLi1013]

Describe the pull request

• What does your PR fix? Fixes [libx264] build failure on linux #14993

Currently, _mp3lame_rel_lib in ../share/mp3lame/mp3lame-config.cmake is like this:

set(_mp3lame_rel_lib "${_mp3lame_root}/lib/libmp3lame..a")
set(_mp3lame_dbg_lib "${_mp3lame_root}/debug/lib/libmp3lame..a")

VCPKG_TARGET_STATIC_LIBRARY_SUFFIX has included ".", it's unnecessary to add it again.

So remove additional "." , only using ${VCPKG_TARGET_STATIC_LIBRARY_SUFFIX} to fix this issue.

Note: No feature needs to test.

[BillyONeal]

Excellent!