REGRESSION (251473@main): [watchOS] Crash when focusing an input fiel…

…d with spellcheck="false"

https://bugs.webkit.org/show_bug.cgi?id=242364
rdar://96458889

Reviewed by Aditya Keerthi.

Add a missing `-respondsToSelector:` check before attempting to set `spellCheckingType`. `spellCheckingType` is an
optional property on the `UITextInputTraits` protocol, and (importantly) isn't implemented on watchOS.

This crash is already exercised by `fast/forms/watchos/enter-text-with-spellcheck-disabled.html`, which (unfortunately)
doesn't run in pre- or post-commit non-internal automation.

* Source/WebKit/UIProcess/ios/WKContentViewInteraction.mm:
(-[WKContentView _updateTextInputTraits:]):

Canonical link: https://commits.webkit.org/252166@main

Source/WebKit/UIProcess/ios/WKContentViewInteraction.mm

@@ -5926,7 +5926,8 @@ - (void)_updateTextInputTraits:(id <UITextInputTraits>)traits
             traits.smartQuotesType = UITextSmartQuotesTypeNo;
         if ([traits respondsToSelector:@selector(setSmartDashesType:)])
             traits.smartDashesType = UITextSmartDashesTypeNo;
-        traits.spellCheckingType = UITextSpellCheckingTypeNo;
+        if ([traits respondsToSelector:@selector(setSpellCheckingType:)])
+            traits.spellCheckingType = UITextSpellCheckingTypeNo;
     }
 
     switch (_focusedElementInformation.inputMode) {