Fix PlayStation build following 278635@main

https://bugs.webkit.org/show_bug.cgi?id=274031

Unreviewed build fix.

278635@main introduced the first usage of `consteval` into the codebase;
apparently this works correctly in clang 9-10 and clang 15+, but not in clang 11-14.

Presumably we should introduce a macro in Compiler.h to allow us to use `consteval` where possible,
but for the moment, this patch just fixes the build by reverting `consteval` to `constexpr`.

* Source/WebCore/css/parser/CSSPropertyParserConsumer+RawTypes.h:
(WebCore::computeMinimumValue):

Canonical link: https://commits.webkit.org/278650@main

Source/WebCore/css/parser/CSSPropertyParserConsumer+RawTypes.h

@@ -93,7 +93,7 @@ struct SymbolRaw {
 NumberRaw replaceSymbol(SymbolRaw, const CSSCalcSymbolTable&);
 template<typename T> T replaceSymbol(T value, const CSSCalcSymbolTable&) { return value; }
 
-consteval double computeMinimumValue(CSSPropertyParserHelpers::IntegerValueRange range)
+constexpr double computeMinimumValue(CSSPropertyParserHelpers::IntegerValueRange range)
 {
     switch (range) {
     case CSSPropertyParserHelpers::IntegerValueRange::All: