Remove unused UIKit SPI

https://bugs.webkit.org/show_bug.cgi?id=259406
rdar://112673362

Reviewed by Wenson Hsieh.

* Source/WebKit/Platform/spi/ios/UIKitSPI.h:

Canonical link: https://commits.webkit.org/266217@main

Source/WebKit/Platform/spi/ios/UIKitSPI.h

@@ -552,8 +552,6 @@ typedef enum {
 @property (nonatomic, readonly, getter=_isHorizontalBouncing) BOOL isHorizontalBouncing;
 @property (nonatomic, readonly, getter=_isAnimatingZoom) BOOL isAnimatingZoom;
 @property (nonatomic, readonly, getter=_isAnimatingScroll) BOOL isAnimatingScroll;
-@property (nonatomic) CGFloat horizontalScrollDecelerationFactor;
-@property (nonatomic) CGFloat verticalScrollDecelerationFactor;
 @property (nonatomic, getter=_contentScrollInset, setter=_setContentScrollInset:) UIEdgeInsets contentScrollInset;
 @property (nonatomic, readonly) UIEdgeInsets _systemContentInset;
 @property (nonatomic, getter=_allowsAsyncScrollEvent, setter=_setAllowsAsyncScrollEvent:) BOOL _allowsAsyncScrollEvent;
@@ -1405,7 +1403,6 @@ typedef NS_ENUM(NSUInteger, _UIScrollDeviceCategory) {
 - (CGFloat)_rubberBandOffsetForOffset:(CGFloat)newOffset maxOffset:(CGFloat)maxOffset minOffset:(CGFloat)minOffset range:(CGFloat)range outside:(BOOL *)outside;
 - (void)_adjustForAutomaticKeyboardInfo:(NSDictionary *)info animated:(BOOL)animated lastAdjustment:(CGFloat*)lastAdjustment;
 - (BOOL)_isScrollingToTop;
-- (CGPoint)_animatedTargetOffset;
 - (BOOL)_canScrollWithoutBouncingX;
 - (BOOL)_canScrollWithoutBouncingY;
 - (void)_setContentOffsetWithDecelerationAnimation:(CGPoint)contentOffset;