Remove six AMD GPUs whose clocks came from game-clock cells

The Wikipedia RDNA/Polaris tables put game and boost clocks in one
"Core / Clock (MHz)" cell, and some rows list only the game clock. The
import read them as base == boost, so the Radeon Pro W7900 Dual Slot,
W7800 48 GB, W6500M, WX 2100/3100 Mobile and RX 6300M records carried
wrong clocks. The page gives no base clock, so drop them.

Author: Seungpyo1007