Use the same quantizers with and without activity masking for 4x4

Since activity masking is off for 4x4 anyway.
video1-short (OD_DISABLE_MASKING=1):
           RATE (%)  DSNR (dB)
    PSNR -0.30016  0.01547
 PSNRHVS -0.59764  0.04352
    SSIM -0.84765  0.03706
FASTSSIM -1.02380  0.05606