wavarc: fix decoding of 16-bit 33kHz stereo samples

[ami_stuff]

./ffmpeg -i 16_33_S_C1.WA -y out.wav
ffmpeg version N-112453-ga7663c9604 Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 11 (Ubuntu 11.4.0-1ubuntu1~22.04)
  configuration: 
  libavutil      58. 27.100 / 58. 27.100
  libavcodec     60. 30.102 / 60. 30.102
  libavformat    60. 15.100 / 60. 15.100
  libavdevice    60.  2.101 / 60.  2.101
  libavfilter     9. 11.100 /  9. 11.100
  libswscale      7.  4.100 /  7.  4.100
  libswresample   4. 11.100 /  4. 11.100
Input #0, wavarc, from '16_33_S_C1.WA':
  Duration: N/A, start: 0.000000, bitrate: N/A
  Stream #0:0: Audio: wavarc (1DIF / 0x46494431), 33333 Hz, stereo, s16p
Stream mapping:
  Stream #0:0 -> #0:0 (wavarc (native) -> pcm_s16le (native))
Press [q] to stop, [?] for help
Output #0, wav, to 'out.wav':
  Metadata:
    ISFT            : Lavf60.15.100
  Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 33333 Hz, stereo, s16, 1066 kb/s
    Metadata:
      encoder         : Lavc60.30.102 pcm_s16le
[out#0/wav @ 0x563654164080] video:0kB audio:1302kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.005850%
size=    1302kB time=00:00:09.99 bitrate=1066.8kbits/s speed= 192x  

[ami_stuff]

it looks like this is a bug in the reference software

"wa32.exe" decompresses correctly only "16_33_S_C0.WA" and "16_33_S_C1.WA" files - CRC OK

(the raw output from decompressed C0 and C1 files (wav) is the same)

but fails to decompress files with other compression modes "16_33_S_C[2/3/4/5].WA" - CRC FAIL

so theoretically "16_33_S_C1.WA" file could be supported correctly by ffmpeg as well