Fix team members API endpoint pagination (#24754)

Fix team members API endpoint pagination (#24754)

Now it's 1-based instead of 0-based

- Fixes #24747

### Before

![image](https://github.com/go-gitea/gitea/assets/20454870/9b58ecfa-666c-4b78-bd0f-93233efeecbd)

### After

![image](https://github.com/go-gitea/gitea/assets/20454870/103b767a-e02e-4473-9f9f-5a676a61c174)

## :warning: BREAKING :warning:
Previous API consumers may have relied on the 0-based pagination of this
endpoint. The page numbering now starts at 1, as documented.

Signed-off-by: Yarden Shoham <git@yardenshoham.com>