tools/target_dec_fuzzer: Adjust threshold for MSZH

Fixes: Timeout (250sec -> 6sec)
Fixes: 17627/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MSZH_fuzzer-5643017129558016

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

tools/target_dec_fuzzer.c

@@ -152,6 +152,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
     case AV_CODEC_ID_LSCR:        maxpixels /= 16; break;
     case AV_CODEC_ID_MOTIONPIXELS:maxpixels /= 256; break;
     case AV_CODEC_ID_MSS2:        maxpixels /= 16384; break;
+    case AV_CODEC_ID_MSZH:        maxpixels /= 128; break;
     case AV_CODEC_ID_SNOW:        maxpixels /= 128; break;
     case AV_CODEC_ID_TRUEMOTION2: maxpixels /= 1024; break;
     case AV_CODEC_ID_VP7:         maxpixels /= 256;  break;