review: fix orphan AVVideo reference after capture backend consolidation

The AVVideo→SCVideo consolidation in 9d242cd moved +displayNames and
+getDisplayName: into SCVideo and deleted av_video.{h,m}, but missed
the +getDisplayName: call in log_display_diagnostic(). With av_video.h
gone, [AVVideo getDisplayName:display_id] no longer compiles.

Switch to [SCVideo getDisplayName:display_id] (which already hosts the
helper after the move).

Author: Nottlespike

src/platform/macos/display.mm

@@ -86,7 +86,7 @@
     }
 
     void log_display_diagnostic(CGDirectDisplayID display_id, const char *source) {
-      NSString *display_name = [AVVideo getDisplayName:display_id];
+      NSString *display_name = [SCVideo getDisplayName:display_id];
       const char *display_name_utf8 = display_name ? display_name.UTF8String : "<unknown>";
       CGDisplayModeRef mode = CGDisplayCopyDisplayMode(display_id);