Make the button for saving theme in the profile primary (elastic#204141)

## Summary
Within the [upcoming EUI update (to use
Borealis)](elastic#199715), we revise
some use cases for colors and component variants associated with them.
In this case, it looks a bit strange and also inconsistent that we are
saving something with success button, so it was changed to primary.
![CleanShot 2024-12-12 at 23 15
50@2x](https://github.com/user-attachments/assets/dcd0185f-69f5-4879-abea-a60c614b9019)

x-pack/plugins/security/public/account_management/user_profile/user_profile.tsx

@@ -1045,7 +1045,7 @@ export const SaveChangesBottomBar: FunctionComponent = () => {
           data-test-subj="saveProfileChangesButton"
           isLoading={formik.isSubmitting}
           isDisabled={formik.submitCount > 0 && !formik.isValid}
-          color="success"
+          color="primary"
           iconType="save"
           fill
         >