[MG_Backend] (DirectGLES): the guard comment cites the visibility block it means

Two comments from the previous commit, corrected. The CMakeLists.txt reference in
DirectGLES.cpp pointed at the link libraries instead of the Debug/Release
visibility preset it names (707-719, not 629-641). The Managers.h note said the
overload is "reached by the pull, verify and push build" through "the three
wrappers", which reads as if all three called it; only
VertexArrayImpl::SyncClientSideVertexArraysForFetch does, and what those flavors
compile is the declaration, which is the point being made.

No code change: the four flavors' libraries are byte-identical to the previous
commit's (comment-only).

MobileGL/MG_Backend/DirectGLES/DirectGLES.cpp

@@ -2423,7 +2423,7 @@ namespace MobileGL::MG_Backend::DirectGLES {
         // function that only re-homes two identical inline blocks the two DrawArrays entry
         // points used to carry. The same spelling governs the three below, and for a second
         // reason on top of the symbol count: a Debug build drops CXX_VISIBILITY_PRESET to
-        // `default` (CMakeLists.txt:629-641), so an external-linkage helper here would be a
+        // `default` (CMakeLists.txt:707-719), so an external-linkage helper here would be a
         // DYNAMIC export in exactly the configuration a symbol gate cannot see it in.
         //
         // ALL FLAVORS, NOT JUST THE SPLIT ARM. These three were inside