[Flagsmith-for-jira] Be more specific on user API key to use

### Is your feature request related to a problem?

As we have multiple Keys (API/SDK/Server-side), it can be confusing what key to use for Jira integrations (user key from account).

Adding more specific screenshots or explanations could help avoiding mistaking what key to use

### Describe the solution you'd like.

Add a screenshot displaying the Account page with the API Key to use for Jira

### Describe alternatives you've considered

Update the wording

### Additional context

_No response_