[net_http_content_disposition_fuzzer] Fix dictionary.

Dictionary mistakenly used "\n" instead of encoding as hex ("\x0a")
causing exceptions on ClusterFuzz.

Bug: 1015442
Change-Id: Id27fb1de4c08ad9fbfc40ddcf1caac915a828259
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1866878Reviewed-by: Matt Menke <mmenke@chromium.org>
Reviewed-by: Asanka Herath <asanka@chromium.org>
Commit-Queue: Matt Menke <mmenke@chromium.org>
Commit-Queue: Asanka Herath <asanka@chromium.org>
Auto-Submit: Jonathan Metzman <metzman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707039}

net/data/fuzzer_dictionaries/net_http_content_disposition_fuzzer.dict

@@ -13,7 +13,10 @@
 " "
 ","
 "''"
-"\n"
+
+# A newline.
+"\x0a"
+
 "?"
 "%"
 "en"