Revert "Increase memory size for media_vpx_video_decoder_fuzzer"

This reverts commit 5cf1517a.

Reason for revert: this change won't work as explained in https://bugs.chromium.org/p/chromium/issues/detail?id=808775#c9 and on clusterfuzz-dev@chromium.org

Original change's description:
> Increase memory size for media_vpx_video_decoder_fuzzer
> 
> The maximum frame size in VP8 is 16,384 x 16,384, which uses most of the
> default 2048 Mb allowed. Bumping up the size to 4096 Mb to handle the larger
> frame size.
> 
> BUG=808775
> TEST=fuzzer test case passes
> 
> Change-Id: I8e1e56bbd0936e745792f34106c7e638ff5a1c2b
> Reviewed-on: https://chromium-review.googlesource.com/1100004
> Reviewed-by: Chrome Cunningham <chcunningham@chromium.org>
> Commit-Queue: John Rummell <jrummell@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#567355}

TBR=jrummell@chromium.org,chcunningham@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 808775
Change-Id: I47d8005442d6b81dcd023a1071e344c2e09304e5
Reviewed-on: https://chromium-review.googlesource.com/1104826Reviewed-by: Max Moroz <mmoroz@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: John Rummell <jrummell@chromium.org>
Commit-Queue: Max Moroz <mmoroz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568209}

media/BUILD.gn

@@ -338,10 +338,7 @@ fuzzer_test("media_vpx_video_decoder_fuzzer") {
     ":media",
     "//base",
   ]
-  libfuzzer_options = [
-    "max_len=400000",
-    "rss_limit_mb=4096",
-  ]
+  libfuzzer_options = [ "max_len = 400000" ]
   seed_corpus = "//media/test/data"
 }