tools/target_dec_fuzzer: Adjust threshold for LSCR

Fixes: Timeout (12sec -> 3sec)
Fixes: 15327/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_LSCR_fuzzer-5702887719567360

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

@@ -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_LSCR:        maxpixels /= 16; break;
     case AV_CODEC_ID_TRUEMOTION2: maxpixels /= 1024; break;
     }