Bump dart from `288dfb3` to `8908ea4` in /app_dart (#2393)

Bumps dart from `288dfb3` to `8908ea4`.

---
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/app_dart/Dockerfile b/app_dart/Dockerfile
index 8290a10..c6c751a 100644
--- a/app_dart/Dockerfile
+++ b/app_dart/Dockerfile
@@ -4,7 +4,7 @@
 
 
 # Dart Docker official images can be found here: https://hub.docker.com/_/dart
-FROM dart:beta@sha256:288dfb322423f4e8d42e2490cf0a3c2a5d802ed3defeb2750509d05f7213b330
+FROM dart:beta@sha256:8908ea48041319fd2ee7a378a71123e72f200c62a88a7bcae5988f3dc886c46a
 
 WORKDIR /app