CMake: Remove duplicate MSVC check

As of this commit, L98 of winconf.cmake already checks for MSVC
before winconf-msvc calls this macro, so we are guaranteed to be
satisfy the check.

cmake/Modules/MacroConfigureMSVCRuntime.cmake

@@ -1,5 +1,4 @@
 macro(configure_msvc_runtime)
-    if(MSVC)
     # Default to statically-linked runtime.
     if("${MSVC_RUNTIME}" STREQUAL "")
         set(MSVC_RUNTIME "static")
@@ -34,5 +33,4 @@ macro(configure_msvc_runtime)
             endif()
         endforeach()
     endif()
-    endif()
 endmacro()