macosx: make sure the fspanel's volume slider knob is entirely displayed and not cut off

(cherry picked from commit 1b6c9901d92a5b000acfa76f30dda85d7c37cd91)

modules/gui/macosx/fspanel.m

@@ -450,9 +450,9 @@
     /* volume slider */
     s_rc = [self frame];
     s_rc.origin.x = 26;
-    s_rc.origin.y = 21;
+    s_rc.origin.y = 20;
     s_rc.size.width = 95;
-    s_rc.size.height = 10;
+    s_rc.size.height = 12;
     o_fs_volumeSlider = [[VLCFSVolumeSlider alloc] initWithFrame: s_rc];
     [o_fs_volumeSlider setMinValue:0];
     [o_fs_volumeSlider setMaxValue:AOUT_VOLUME_MAX];