Fix status codes and response messages for PUT in API docs

[tsutsu3]

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[yubiuser]

It seems, response code can be 200 if the item is updated, but 201 if the item is newly created.

https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods/PUT

__

Did you check, which response is actually used by FTL when a) an update happend and b) a new item is created?

[tsutsu3]

I have checked the response in WebUI's /api/docs.
Additionally, I reviewed the following logic in list.c:

int response_code = 201; // 201 - Created
if(api->method == HTTP_PUT)
    response_code = 200; // 200 - OK

From this, it appears that a PUT request always returns a 200 OK response, regardless of whether an item was created or updated.

Given this behavior, I believe the appropriate description should be Created or Updated Item to accurately reflect the response.

[tsutsu3]

If the expected behavior is to return 201 Created for new item creation and 200 OK for updates, please feel free to close this PR.

[DL6ER]

The documentation is obviously out-of-sync with the actual code. Your PR fixes that.