Roll ICU to c52a2a25

This roll includes only one change to fix
BCP 47 language tag validation for v8.

https://chromium.googlesource.com/chromium/deps/icu/+/c52a2a25

TBR=gsathya@chromium.org

Bug: v8:8135
Test: v8 - test262/intl402/Locale/constructor-unicode-ext-valid
Change-Id: Ida7ed667898c25d4cec6ff20c86d87e07b962c5a
Reviewed-on: https://chromium-review.googlesource.com/1238469Reviewed-by: Jungshik Shin <jshin@chromium.org>
Commit-Queue: Jungshik Shin <jshin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593209}

DEPS

@@ -761,7 +761,7 @@ deps = {
     Var('chromium_git') + '/chromium/deps/hunspell_dictionaries.git' + '@' + 'a9bac57ce6c9d390a52ebaad3259f5fdb871210e',
 
   'src/third_party/icu':
-    Var('chromium_git') + '/chromium/deps/icu.git' + '@' + '7ca3ffa77d635e44b9735e1b54fb9c4da3b6c821',
+    Var('chromium_git') + '/chromium/deps/icu.git' + '@' + 'c52a2a250d6c5f5cbdd015dff36af7c5d0ae1150',
 
   'src/third_party/icu4j': {
       'packages': [