avfilter/vf_gblur: Remove unnecessary emms_c()

There is no MMX ASM code for gblur.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavfilter/vf_gblur.c

@@ -73,7 +73,6 @@ static int filter_horizontally(AVFilterContext *ctx, void *arg, int jobnr, int n
 
     s->horiz_slice(buffer + width * slice_start, width, slice_end - slice_start,
                    steps, nu, boundaryscale, localbuf);
-    emms_c();
     return 0;
 }