Wizard: Remove clear handler from Release select on Image Output step

This commit fixes #893 by removing the ability to clear the release
select on the image output step (this is the select where the user
chooses from RHEL 8, RHEL 9, CentOS 8 or 9, etc...).

Originally the ability to clear the select was added so that the default
state (where CentOS options are hidden behind a 'speedbump') could be
returned to but this seems unnecessary in retrospect and introduces
opportunities for bugs (as seen with the validation in #893) so it seems
wise to simply remove the ability to clear altogether.

src/Components/CreateImageWizard/formComponents/ImageOutputReleaseSelect.js

@@ -24,11 +24,6 @@ const ImageOutputReleaseSelect = ({ label, isRequired, ...props }) => {
     setIsOpen(false);
   };
 
-  const handleClear = () => {
-    change(input.name, null);
-    setShowDevelopmentOptions(false);
-  };
-
   const handleExpand = () => {
     setShowDevelopmentOptions(true);
   };
@@ -39,7 +34,6 @@ const ImageOutputReleaseSelect = ({ label, isRequired, ...props }) => {
         variant={SelectVariant.single}
         onToggle={() => setIsOpen(!isOpen)}
         onSelect={setRelease}
-        onClear={handleClear}
         selections={RELEASES[getState()?.values?.[input.name]]}
         isOpen={isOpen}
         {...(!showDevelopmentOptions && {