tools/target_dec_fuzzer: increase snows threshold

snow allows creating large output from tiny input, like other
wavelet codecs

Fixes: Timeout (82sec -> 1.5sec)
Fixes: 9520/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SNOW_fuzzer-6286612576075776

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

tools/target_dec_fuzzer.c

@@ -141,6 +141,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
     case AV_CODEC_ID_INDEO4:    maxpixels /= 128; break;
     case AV_CODEC_ID_LSCR:        maxpixels /= 16; break;
     case AV_CODEC_ID_MOTIONPIXELS:maxpixels /= 256; break;
+    case AV_CODEC_ID_SNOW:        maxpixels /= 128; break;
     case AV_CODEC_ID_TRUEMOTION2: maxpixels /= 1024; break;
     }