Merge pull request #3870 from dart-lang/release

linter 1.31.0 cherry-pick release (update)
diff --git a/CHANGELOG.md b/CHANGELOG.md
index a9a2c65..e60ecc1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 - updated `prefer_equal_for_default_values` to not report for SDKs `>=2.19`,
   where this lint is now an analyzer diagnostic.
+- updated `unrelated_type_equality_checks` to support updated `package:fixnum`
+  structure.
 
 # 1.30.0