Update the ICU DEPS entry to match version used by Flutter.

The one we're using is over a year older than the one they're using,
so let's try to limit any discrepancies that might happen between
our uses and theirs.

Bug: dart-lang/sdk#40850
Change-Id: I0e89c821470ea46e2bc807d33c7f1b6a24aa1e65
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/142840
Auto-Submit: Tess Strickland <sstrickl@google.com>
Commit-Queue: Martin Kustermann <kustermann@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>

Author: sstrickl

DEPS

@@ -97,7 +97,7 @@ vars = {
   "http_retry_tag": "0.1.1",
   "http_tag" : "0.12.0+2",
   "http_throttle_tag" : "1.0.2",
-  "icu_rev" : "c56c671998902fcc4fc9ace88c83daa99f980793",
+  "icu_rev" : "5005010d694e16571b8dfbf07d70817841f80a69",
   "idl_parser_rev": "5fb1ebf49d235b5a70c9f49047e83b0654031eb7",
   "intl_tag": "0.16.1",
   "jinja2_rev": "2222b31554f03e62600cd7e383376a7c187967a1",