tools/target_dem_fuzzer.c: Decrease maxblocks

Fixes: Timeout
Fixes: 28606/clusterfuzz-testcase-minimized-ffmpeg_dem_FRM_fuzzer-5123311424110592
Fixes: 28796/clusterfuzz-testcase-minimized-ffmpeg_dem_R3D_fuzzer-5945803411685376
Fixes: 28821/clusterfuzz-testcase-minimized-ffmpeg_dem_BRSTM_fuzzer-6044239834251264
Fixes: 28841/clusterfuzz-testcase-minimized-ffmpeg_dem_SIFF_fuzzer-5485368388485120
Fixes: 28862/clusterfuzz-testcase-minimized-ffmpeg_dem_AST_fuzzer-5081306790756352

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_dem_fuzzer.c

@@ -88,7 +88,7 @@ static int64_t io_seek(void *opaque, int64_t offset, int whence)
 
 // Ensure we don't loop forever
 const uint32_t maxiteration = 8096;
-const int maxblocks= 100000;
+const int maxblocks= 50000;
 
 static const uint64_t FUZZ_TAG = 0x4741542D5A5A5546ULL;