Update @font-palette-values override-colors order

https://bugs.webkit.org/show_bug.cgi?id=246565
rdar://problem/101216288

Reviewed by Tim Nguyen.

* LayoutTests/TestExpectations: Removed failure expectation.

* Source/WebCore/platform/graphics/cocoa/FontCacheCoreText.cpp:
(WebCore::addAttributesForCustomFontPalettes): Use CFDictionarySetValue, which overwrites
existing values, resulting in "last one wins".

Canonical link: https://commits.webkit.org/255604@main

LayoutTests/TestExpectations

@@ -3757,7 +3757,6 @@ webkit.org/b/206881 imported/w3c/web-platform-tests/css/css-fonts/font-face-weig
 webkit.org/b/206881 imported/w3c/web-platform-tests/css/css-fonts/font-face-weight-default-variable.html [ ImageOnlyFailure ]
 
 # Triaged css-fonts failures
-webkit.org/b/246565 imported/w3c/web-platform-tests/css/css-fonts/font-palette-21.html [ ImageOnlyFailure ]
 webkit.org/b/246564 imported/w3c/web-platform-tests/css/css-fonts/font-synthesis-small-caps-not-applied.html [ ImageOnlyFailure ]
 
 # vert font feature in vertical-text

Source/WebCore/platform/graphics/cocoa/FontCacheCoreText.cpp

@@ -540,7 +540,7 @@ static void addAttributesForCustomFontPalettes(CFMutableDictionaryRef attributes
             int64_t rawIndex = pair.first; // There is no kCFNumberUIntType.
             auto number = adoptCF(CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt64Type, &rawIndex));
             auto colorObject = cachedCGColor(color);
-            CFDictionaryAddValue(overrideDictionary.get(), number.get(), colorObject.get());
+            CFDictionarySetValue(overrideDictionary.get(), number.get(), colorObject.get());
         }
         if (CFDictionaryGetCount(overrideDictionary.get()))
             CFDictionaryAddValue(attributes, kCTFontPaletteColorsAttribute, overrideDictionary.get());