Make OptionSet bool operator const

https://bugs.webkit.org/show_bug.cgi?id=259050

Reviewed by Darin Adler.

Make OptionSet bool operator const.

* Source/WTF/wtf/OptionSet.h:
(WTF::OptionSet::operator bool const):
(WTF::OptionSet::operator bool): Deleted.

Canonical link: https://commits.webkit.org/265905@main

Source/WTF/wtf/OptionSet.h

@@ -160,7 +160,7 @@ template<typename E> class OptionSet {
     constexpr iterator begin() const { return m_storage; }
     constexpr iterator end() const { return 0; }
 
-    constexpr explicit operator bool() { return !isEmpty(); }
+    constexpr explicit operator bool() const { return !isEmpty(); }
 
     constexpr bool contains(E option) const
     {