It shows what you are talking about on page 8C-3 of the shop manual (pdf page 13320). The circuit diagram on page 8D-20 (pdf page 13343) does not. It's probably OK to just leave it disconnected.

You may want to see if it's got 12V on it (it may be the power lead for an amplified antenna) so make sure you tape it off so that it doesn't ground.