macosx: Fix whitespace in collection view item if

Fixes compile warning:

/Users/claucambra/Downloads/GitRepos/vlc/extras/package/macosx/../../../modules/gui/macosx/library/VLCLibraryCollectionViewItem.m:230:62: warning: treating Unicode character as whitespace [-Wunicode-whitespace]
        if (mediaItem.mediaType == VLC_ML_MEDIA_TYPE_VIDEO || mediaItem.mediaType == VLC_ML_MEDIA_TYPE_UNKNOWN) {
                                                             ^

Signed-off-by: Claudio Cambra developer@claudiocambra.com