Either A) Phasma lowers the shields and also gives them the map. Maybe you could generate a shot of the screen where we see the shield lowering, and then later when she stands, we see the galaxy map on the screen, or vice versa.

Or B) there is no planetary shield, and Phasma just gives them the map (and possibly sounds the alarm). Black Squadron is either trying to destroy Starkiller (the weapon or the forge), or they are purely a distraction for Han & Finn. The oscillator could be turned into a tractor beam generator as well that they have to destroy.

EDIT: Han might say shield during the briefing scene. He mentions the shields having a fractional refresh rate during the hyperspace scene, but that can be cut, since later he says, “If we go any higher they’ll see us!”

Han during the the “that’s not how the Force works!” scene, he says “Then how do you know how to disable the shields?” That can be cut.

The only time it might be a problem is that when they get inside the base, he does say, “The shields?” and Finn in the same shot says, “I have an idea.” Either you could use some effect to make him not say anything. Or just cut that interaction and we can assume Finn figured something out. Or move that “I have an idea” line, to later. Or possibly cut to a different shot, maybe a cutaway to Chewie if possible, to remove that “shields” line. Removing any mention of the shields is possible I think.