Update dart_style to 1.2.6.

Change-Id: I82036fa3babc65ffa96f56309b073dd72f07c6f6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/98695
Commit-Queue: Kevin Moore <kevmoo@google.com>
Reviewed-by: Kevin Moore <kevmoo@google.com>
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 29f220f..5ad463c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,12 @@
+## 2.2.1-dev.3.1
+
+#### dartfmt
+
+*   Tweak set literal formatting to follow other collection literals.
+*   Add support for "UI as code" features.
+*   Properly format trailing commas in assertions.
+*   Improve indentation of adjacent strings in argument lists.
+
 ## 2.2.1-dev.3.0
 
 ### Core library changes
diff --git a/DEPS b/DEPS
index cc1d44e..12a540e 100644
--- a/DEPS
+++ b/DEPS
@@ -79,7 +79,7 @@
   #     and land the review.
   #
   # For more details, see https://github.com/dart-lang/sdk/issues/30164
-  "dart_style_tag": "1.2.5",  # Please see the note above before updating.
+  "dart_style_tag": "1.2.6",  # Please see the note above before updating.
 
   "dartdoc_tag" : "v0.28.2",
   "fixnum_tag": "0.10.9",