Roll ICU to a191af9d

This roll has only one change as recorded in
     https://chromium.googlesource.com/chromium/deps/icu/+/a191af9d .

TBR=gsathya@chromium.org

Bug: chromium: 870338
Test: See the bug
Change-Id: Iceaa255ede13ef3f9e94fdcf6ab74268c1940427
Reviewed-on: https://chromium-review.googlesource.com/1184508Reviewed-by: Jungshik Shin <jshin@chromium.org>
Commit-Queue: Jungshik Shin <jshin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585291}

DEPS

@@ -750,7 +750,7 @@ deps = {
     Var('chromium_git') + '/chromium/deps/hunspell_dictionaries.git' + '@' + 'a9bac57ce6c9d390a52ebaad3259f5fdb871210e',
 
   'src/third_party/icu':
-    Var('chromium_git') + '/chromium/deps/icu.git' + '@' + '297a4dd02b9d36c92ab9b4f121e433c9c3bc14f8',
+    Var('chromium_git') + '/chromium/deps/icu.git' + '@' + 'a191af9d025859e8368b8b469120d78006e9f5f6',
 
   'src/third_party/icu4j': {
       'packages': [