tools/target_dec_fuzzer: Adjust threshold for theora

Fixes: Timeout
Fixes: 33916/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_THEORA_fuzzer-4620863119949824

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

@@ -195,7 +195,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
     case AV_CODEC_ID_SNOW:        maxpixels  /= 128;   break;
     case AV_CODEC_ID_TAK:         maxsamples /= 1024;  break;
     case AV_CODEC_ID_TGV:         maxpixels  /= 32;    break;
-    case AV_CODEC_ID_THEORA:      maxpixels  /= 1024;  break;
+    case AV_CODEC_ID_THEORA:      maxpixels  /= 16384; break;
     case AV_CODEC_ID_TRUEMOTION2: maxpixels  /= 1024;  break;
     case AV_CODEC_ID_TSCC:        maxpixels  /= 1024;  break;
     case AV_CODEC_ID_VC1IMAGE:    maxpixels  /= 8192;  break;