The first reply is correct, this has nothing to do with the firmware. Firmware is what's installed into the phantom itself. This is a message about the app version for dji go on you tablet.
This update they are forcing is to fix that fly away issue, which existed only on version 3.1.2. If you have an older version, you are fine. If you have 3.1.2, you absolutely want to get something else, even the newer version is better.
If you have android, I posted a solution over in the general discussion forum that allows you to keep an older version. But you might as well just let it update. Anything is better than letting it keep 3.1.2 on your tablet
P3A with Nvidia Shield K1 tablet