Roll third_party/icu/ 1b7d391f0..2c51e5cc7 (3 commits)

https://chromium.googlesource.com/chromium/deps/icu.git/+log/1b7d391f0528..2c51e5cc7e0a

Created with:
  roll-dep third_party/icu

Change-Id: I8056118ee597ba3177f7c02378c209999e98a6ab
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/103091
Commit-Queue: Lei Zhang <thestig@chromium.org>
Auto-Submit: Nigi <nigi@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
diff --git a/DEPS b/DEPS
index dc0edc4..fff099b 100644
--- a/DEPS
+++ b/DEPS
@@ -86,7 +86,7 @@
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling icu
   # and whatever else without interference from each other.
-  'icu_revision': '1b7d391f0528fb3a4976b7541b387ee04f915f83',
+  'icu_revision': '2c51e5cc7e0a06cd4cd7cb2ddbac445af9b475ba',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling instrumented_lib
   # and whatever else without interference from each other.