Bump dart from `bab342b` to `bf47ad9` in /auto_submit (#2370)

Bumps dart from `bab342b` to `bf47ad9`.

---
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 1fc49c3..18a1c02 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:bab342b08fff246c29226f3403e54b69b00316546decd3350c6975fb1480187f
+FROM dart:beta@sha256:bf47ad95b5051c20a0822180963b237a53f53c5b5a671949e4731240d3112df8
 
 WORKDIR /app