Revert "cocoa: Discard the IME Candidate Window immediately when Escape is pressed"

This reverts commit 0d76e2a8a1a8e6a2801123587c2205a288d49406, as it introduced other issues:
https://github.com/libsdl-org/SDL/pull/6486#issuecomment-1304684865

src/video/cocoa/SDL_cocoakeyboard.m

@@ -180,13 +180,6 @@
     return [NSArray array];
 }
 
-// Discard the IME Candidate Window
-- (void)cancelOperation:(id)sender
-{
-    [[self inputContext] discardMarkedText];
-    [self unmarkText];
-}
-
 @end
 
 static void
@@ -415,11 +408,6 @@ Cocoa_HandleKeyEvent(_THIS, NSEvent *event)
             SDL_Log("The key you just pressed is not recognized by SDL. To help get this fixed, report this to the SDL forums/mailing list <https://discourse.libsdl.org/> or to Christian Walther <cwalther@gmx.ch>. Mac virtual key code is %d.\n", scancode);
         }
 #endif
-        /* Discard the IME Candidate Window immediately */
-        if (code == SDL_SCANCODE_ESCAPE) {
-            [data.fieldEdit cancelOperation:NULL];
-        }
-
         if (SDL_EventState(SDL_TEXTINPUT, SDL_QUERY)) {
             /* FIXME CW 2007-08-16: only send those events to the field editor for which we actually want text events, not e.g. esc or function keys. Arrow keys in particular seem to produce crashes sometimes. */
             [data.fieldEdit interpretKeyEvents:[NSArray arrayWithObject:event]];