tools/target_dec_fuzzer: Adjust maxpixels for G2M

Fixes: Timeout (50sec -> 3sec)
Fixes: 27383/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_G2M_fuzzer-5196953666977792

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

@@ -150,7 +150,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
     case AV_CODEC_ID_DST:         maxsamples /= 1<<20; break;
     case AV_CODEC_ID_DXV:         maxpixels  /= 32;    break;
     case AV_CODEC_ID_FFWAVESYNTH: maxsamples /= 16384; break;
-    case AV_CODEC_ID_G2M:         maxpixels  /= 64;    break;
+    case AV_CODEC_ID_G2M:         maxpixels  /= 1024;  break;
     case AV_CODEC_ID_GDV:         maxpixels  /= 512;   break;
     case AV_CODEC_ID_GIF:         maxpixels  /= 16;    break;
     case AV_CODEC_ID_HAP:         maxpixels  /= 128;   break;