Bump dart from `d13041c` to `2d8257b` in /auto_submit (#2311)

Bumps dart from `d13041c` to `2d8257b`.

---
updated-dependencies:
- dependency-name: dart
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
diff --git a/auto_submit/Dockerfile b/auto_submit/Dockerfile
index 859ed0f..39e4b3d 100644
--- a/auto_submit/Dockerfile
+++ b/auto_submit/Dockerfile
@@ -4,7 +4,7 @@
 
 
 # Dart Docker official images can be found here: https://hub.docker.com/_/dart
-FROM dart:beta@sha256:d13041c0552853a14cc543b7df21ea01cb484ea7607901ee2138c02bd9ec5283
+FROM dart:beta@sha256:2d8257b23e5a247ea51d24b31689aaf5ec571a077cc0db3978bc67567b04d2ca
 
 WORKDIR /app