Incorrect and incomplete inline docs for wp_check_browser_version()

[coffee2code]

The inline docs for wp_check_browser_version() in wp-admin/includes/dashboard.php incorrectly states that the response array from the BrowseHappy API will include the upgrade_url key. In reality, the name for the key is update_url. (The correct key name is used in the actual code.)

See ​https://meta.trac.wordpress.org/browser/sites/trunk/api.wordpress.org/public_html/core/browse-happy/1.0/parse.php#L83

Additionally, the API may return a platform key and value, which isn't mentioned in the inline docs.

The attached patch corrects the misnamed response key and adds docs for the missing key.

[coffee2code]

Patch to correct misnamed key and add docs for omitted key

[SergeyBiryukov]

In 40822:

Administration: Update the docs for wp_check_browser_version().

Correct update_url key name, add missing platform key.

Props coffee2code.
Fixes #40839.