fix(webhook): clarify endpoint expects application/json payloads (#13786)

This PR updates the subtitle under the "Endpoint URL" input on the
webhook creation form.

The updated text clearly states that the server sends POST requests with
application/json and recommends setting the correct Content-Type.

This addresses issue #13757.

Closes #13757

---------

Co-authored-by: Charles Bochet <charlesBochet@users.noreply.github.com>
Co-authored-by: ehconitin <nitinkoche03@gmail.com>

packages/twenty-front/src/modules/settings/developers/components/SettingsDevelopersWebhookForm.tsx

@@ -149,7 +149,7 @@ export const SettingsDevelopersWebhookForm = ({
           <Section>
             <H2Title
               title={t`Endpoint URL`}
-              description={t`We will send POST requests to this endpoint for every new event`}
+              description={t`We will send a POST request to this endpoint for each new event in application/json format`}
             />
             <Controller
               name="targetUrl"