tools/target_dec_fuzzer: adjust pixel threshold for TRUEMOTION2, as it allows...

tools/target_dec_fuzzer: adjust pixel threshold for TRUEMOTION2, as it allows coding gigantic images on tiny input

Fixes: Timeout (137sec -> 6sec)
Fixes: 16090/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_TRUEMOTION2_fuzzer-5674245178261504

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

@@ -139,6 +139,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
     case AV_CODEC_ID_HNM4_VIDEO:maxpixels /= 128; break;
         // Cliping in C, generally slow even with small input
     case AV_CODEC_ID_INDEO4:    maxpixels /= 128; break;
+    case AV_CODEC_ID_TRUEMOTION2: maxpixels /= 1024; break;
     }