Remove outdated libs_version.txt file (#14631)

This is not being synced with changes done in github.com/winlibs and
served only for documentation purposes. Since the list is outdated it is
simpler to remove it than maintain it updated.

Author: petk

UPGRADING.INTERNALS

@@ -171,6 +171,7 @@ PHP 8.4 INTERNALS UPGRADE NOTES
    - The HAVE_OPENSSL_EXT symbol is now consistently defined to value 1 whether
      the openssl extension is available either as shared or built statically.
    - Added configure option --enable-phpdbg-debug to build phpdbg in debug mode.
+   - The win32/build/libs_version.txt file has been removed.
 
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 3. Module changes