Reduce input size limit of parser fuzzer to 2kB

R=mmoroz@chromium.org

Bug: chromium:911644
Change-Id: Icc42e5ace80ea816925c95e2ea330b484b68e7cf
Reviewed-on: https://chromium-review.googlesource.com/c/1379878
Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58280}

test/fuzzer/parser.cc

@@ -19,7 +19,7 @@
 
 bool IsValidInput(const uint8_t* data, size_t size) {
   // Ignore too long inputs as they tend to find OOM or timeouts, not real bugs.
-  if (size > 8192) {
+  if (size > 2048) {
     return false;
   }