feat(explore-popover): Show disabled 'Save' button in explore popover (#21318)

Co-authored-by: Herbert Gainor <herbert.gainor@preset.io>
Co-authored-by: Michael S. Molina <michael.s.molina@gmail.com>

superset-frontend/src/explore/components/controls/DndColumnSelectControl/ColumnSelectPopover.tsx

@@ -406,10 +406,8 @@ const ColumnSelectPopover = ({
           {t('Close')}
         </Button>
         <Button
-          disabled={!stateIsValid}
-          buttonStyle={
-            hasUnsavedChanges && stateIsValid ? 'primary' : 'default'
-          }
+          disabled={!stateIsValid || !hasUnsavedChanges}
+          buttonStyle="primary"
           buttonSize="small"
           onClick={onSave}
           data-test="ColumnEdit#save"