chore: fix button styling (#1132)

**Description:**

This PR fixes the button styling issue

**Before:**


![image](https://github.com/documenso/documenso/assets/23498248/0af045aa-3714-48d8-9c22-6cd171b07079)

**After:**

<img width="1280" alt="Screenshot 2024-04-30 at 6 48 47 PM"
src="https://github.com/documenso/documenso/assets/23498248/e7dd99de-60fc-4cc2-aefc-21b130aa0116">

packages/ui/primitives/template-flow/add-template-placeholder-recipients.tsx

@@ -282,6 +282,7 @@ export const AddTemplatePlaceholderRecipientsFormPartial = ({
           <Button
             type="button"
             className="dark:bg-muted dark:hover:bg-muted/80 bg-black/5 hover:bg-black/10"
+            variant="secondary"
             disabled={
               isSubmitting || getValues('signers').some((signer) => signer.email === user?.email)
             }