Remove a few functions in AbstractPosts (#25008)

* Remove unnecessary Core Data property setters

The functions were originally added in commit 32477e1.
The original implementation needed to update another property in the setters.
But the update code no longer exists, and the override method becomes redundant,
since it's the same as the default Core Data implementation.

* Remove AbstractPost.setDateCreated

The same function exists in the super class BasePost.

Author: crazytonyli

Sources/WordPressData/Objective-C/AbstractPost.m

@@ -35,30 +35,6 @@ - (void)save
     [[ContextManager sharedInstance] saveContext:self.managedObjectContext];
 }
 
-
-#pragma mark - Getters/Setters
-
-- (void)setRemoteStatusNumber:(NSNumber *)remoteStatusNumber
-{
-    NSString *key = @"remoteStatusNumber";
-    [self willChangeValueForKey:key];
-    [self setPrimitiveValue:remoteStatusNumber forKey:key];
-    [self didChangeValueForKey:key];
-}
-
-- (void)setDate_created_gmt:(NSDate *)date_created_gmt
-{
-    NSString *key = @"date_created_gmt";
-    [self willChangeValueForKey:key];
-    [self setPrimitiveValue:date_created_gmt forKey:key];
-    [self didChangeValueForKey:key];
-}
-
-- (void)setDateCreated:(NSDate *)localDate
-{
-    self.date_created_gmt = localDate;
-}
-
 #pragma mark -
 #pragma mark Revision management