Bump dart from `7b1b5c8` to `4c77cf9` in /auto_submit (#2450)

Bumps dart from `7b1b5c8` to `4c77cf9`.

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

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 af3b0c1..4123478 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@sha256:7b1b5c83b549a6410a3f89a54ec3f702ec0cbe6ac5e8fc02b1bdc0970a6cba73
+FROM dart:beta@sha256:4c77cf9c98c527de9df411da60c0f85195dfed20d48e19885ff69f2bd9a5ebb0
 
 WORKDIR /app