Remove hunspell_dictionaries from chrome/test:unit_tests data.

Not necessary since spellcheck was componentized.

Bug: 791632
Change-Id: I442a50cc15d1fc63714f65a2abbf62b8b254938c
Reviewed-on: https://chromium-review.googlesource.com/808984Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: John Budorick <jbudorick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#522330}

chrome/test/BUILD.gn

@@ -2559,7 +2559,6 @@ test("unit_tests") {
     "//net/tools/testserver/",
     "//third_party/accessibility-audit/axs_testing.js",
     "//third_party/chaijs/chai.js",
-    "//third_party/hunspell_dictionaries/",
     "//third_party/pyftpdlib/",
     "//third_party/pywebsocket/",
     "//third_party/tlslite/",