Updated version for third_party/pkg/intl
Updated version for third_party/pkg/intl

The new version 0.16.1 does not use `fromEnvironment` constructors,
whereas the old version 0.15.7 does use it, and 0.15.7 uses it in a way
which requires updates in order to keep working when the breaking
change #40678 is landed.

Change-Id: I10cabc2d7799c448f7b42d88e24bb8406fcf0672
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/140604
Reviewed-by: Alexander Thomas <29642742b6693024c89de8232f2e2542cf7eedf7@google.com>
Commit-Queue: Erik Ernst <251bb01623bfda2cd9151e339a6e783ca432874c@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk