Correct corner radius for macOS to match iOS.

https://bugs.webkit.org/show_bug.cgi?id=293011
rdar://149900197

Reviewed by Aditya Keerthi.

On iOS we have an overlay for the find indicator
that adds a corner radius to the indicator. We should
just do this for all TextIndicators on all cocoa platforms.

* Source/WebCore/page/cocoa/WebTextIndicatorLayer.mm:

Canonical link: https://commits.webkit.org/294932@main

Author: megangardner

Source/WebCore/page/cocoa/WebTextIndicatorLayer.mm

@@ -44,7 +44,7 @@
 constexpr CFTimeInterval fadeOutAnimationDuration = 0.3;
 
 constexpr CGFloat borderWidth = 0;
-constexpr CGFloat cornerRadius = 0;
+constexpr CGFloat cornerRadius = 3;
 constexpr CGFloat dropShadowOffsetX = 0;
 constexpr CGFloat dropShadowOffsetY = 1;