devel/git: helpful description for CURL option

Turning off CURL OPTIONS knob has somewhat unexpected consequences, ie.
disables HTTPS transport, thus no Github access.

This is not evident from the default option description. The tiny patch
adds non standard knob description specifically mentioning HTTPS
unavailability, when it gets turned off.

While here, sort *_DESC variables alphabetically.

PR: 242682
Submitted by: Piotr Smyrak <ps.ports@smyrak.com>
Sponsored by: Rubicon Communications, LLC (Netgate)