tools/target_dec_fuzzer: Adjust threshold for RASC

Fixes: Timeout(35sec -> 4sec)
Fixes: 19289/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_RASC_fuzzer-5676526398078976

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

@@ -145,6 +145,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
     case AV_CODEC_ID_FFWAVESYNTH: maxsamples /= 16384; break;
     case AV_CODEC_ID_MSRLE:     maxpixels /= 16;  break;
     case AV_CODEC_ID_QTRLE:     maxpixels /= 16;  break;
+    case AV_CODEC_ID_RASC:      maxpixels /= 16;  break;
     case AV_CODEC_ID_SANM:      maxpixels /= 16;  break;
     case AV_CODEC_ID_G2M:       maxpixels /= 64;  break;
     case AV_CODEC_ID_GIF:       maxpixels /= 16;  break;