MKV configure: remove outdated workaround for MacOS

(cherry picked from commit fe025033)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

configure.ac

@@ -2206,9 +2206,6 @@ if test "${enable_mkv}" != "no" -a "${CXX}" != ""; then
             [AC_MSG_RESULT([yes])
               AC_CHECK_HEADERS(matroska/KaxAttachments.h)
               VLC_ADD_CXXFLAGS([mkv],[])
-              if test "${SYS}" = "darwin"; then
-                VLC_ADD_CXXFLAGS([mkv],[-O1])
-              fi
               AC_CHECK_LIB(ebml_pic, main, [
                 VLC_ADD_PLUGIN([mkv])
                 VLC_ADD_LIBS([mkv],[-lmatroska -lebml_pic])