macOS: removed deprecated UpdateSystemActivity() call.

The non-deprecated approach (IOPMAssertion) already exists in SDL, and is
available in Mac OS X 10.6 and later (although it was incorrectly listed as
10.7 and later in SDL). Since SDL now requires 10.6 or later, this is no
longer conditionally used.

src/video/cocoa/SDL_cocoaevents.m

@@ -394,17 +394,6 @@ - (BOOL)application:(NSApplication *)theApplication openFile:(NSString *)filenam
 Cocoa_PumpEvents(_THIS)
 { @autoreleasepool
 {
-    /* Update activity every 30 seconds to prevent screensaver */
-    SDL_VideoData *data = (SDL_VideoData *)_this->driverdata;
-    if (_this->suspend_screensaver && !data->screensaver_use_iopm) {
-        Uint32 now = SDL_GetTicks();
-        if (!data->screensaver_activity ||
-            SDL_TICKS_PASSED(now, data->screensaver_activity + 30000)) {
-            UpdateSystemActivity(UsrActivity);
-            data->screensaver_activity = now;
-        }
-    }
-
     for ( ; ; ) {
         NSEvent *event = [NSApp nextEventMatchingMask:NSAnyEventMask untilDate:[NSDate distantPast] inMode:NSDefaultRunLoopMode dequeue:YES ];
         if ( event == nil ) {
@@ -426,10 +415,6 @@ - (BOOL)application:(NSApplication *)theApplication openFile:(NSString *)filenam
 {
     SDL_VideoData *data = (SDL_VideoData *)_this->driverdata;
 
-    if (!data->screensaver_use_iopm) {
-        return;
-    }
-
     if (data->screensaver_assertion) {
         IOPMAssertionRelease(data->screensaver_assertion);
         data->screensaver_assertion = 0;

src/video/cocoa/SDL_cocoavideo.h

@@ -52,7 +52,6 @@ typedef struct SDL_VideoData
     SDLTranslatorResponder *fieldEdit;
     NSInteger clipboard_count;
     Uint32 screensaver_activity;
-    BOOL screensaver_use_iopm;
     IOPMAssertionID screensaver_assertion;
 
 } SDL_VideoData;

src/video/cocoa/SDL_cocoavideo.m

@@ -152,9 +152,6 @@
 
     data->allow_spaces = ((floor(NSAppKitVersionNumber) > NSAppKitVersionNumber10_6) && SDL_GetHintBoolean(SDL_HINT_VIDEO_MAC_FULLSCREEN_SPACES, SDL_TRUE));
 
-    /* The IOPM assertion API can disable the screensaver as of 10.7. */
-    data->screensaver_use_iopm = floor(NSAppKitVersionNumber) > NSAppKitVersionNumber10_6;
-
     return 0;
 }