Remove the unnecessary OR operation while getting the content type in `getData` (#7604)

It looks like inside the `getData` function we are getting the
`contentType` from the header. But while doing it, we have a weird
`''.startsWith('text/html');` after an OR operator. I think this might
be a forgotten artifact while refactoring that code.
`''.startsWith('text/html');` always returns false, which was confusing
to me while I was looking at this function. And below that line, we have
a check for `contentType` to see if it's "application/json".

See:
eccd74e32e/ui/helpers/http.js (L24)

ui/helpers/http.js

@@ -18,8 +18,7 @@ export const getData = async function getData(url, options = {}) {
     failureStatus = response.status;
   }
 
-  const contentType =
-    response.headers.get('content-type') || ''.startsWith('text/html');
+  const contentType = response.headers.get('content-type');
 
   if (contentType && contentType !== 'application/json' && failureStatus) {
     const errorMessage = processErrorMessage(