tools/target_dec_fuzzer: Adjust threshold for MTS2

Fixes: Timeout
Fixes: 50030/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MTS2_fuzzer-5767793731043328

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

@@ -254,6 +254,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
     case AV_CODEC_ID_MSRLE:       maxpixels  /= 16;    break;
     case AV_CODEC_ID_MSS2:        maxpixels  /= 16384; break;
     case AV_CODEC_ID_MSZH:        maxpixels  /= 128;   break;
+    case AV_CODEC_ID_MTS2:        maxpixels  /= 4096;  break;
     case AV_CODEC_ID_MVC2:        maxpixels  /= 128;   break;
     case AV_CODEC_ID_MWSC:        maxpixels  /= 256;   break;
     case AV_CODEC_ID_MXPEG:       maxpixels  /= 128;   break;