Bump flutter_markdown from 0.6.12 to 0.6.13 in /zxscanner

Bumps [flutter_markdown](https://github.com/flutter/packages/tree/main/packages) from 0.6.12 to 0.6.13.
- [Release notes](https://github.com/flutter/packages/releases)
- [Commits](https://github.com/flutter/packages/commits/flutter_markdown-v0.6.13/packages)

---
updated-dependencies:
- dependency-name: flutter_markdown
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

zxscanner/pubspec.lock

@@ -283,7 +283,7 @@ packages:
       name: flutter_markdown
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.6.12"
+    version: "0.6.13"
   flutter_mobx:
     dependency: "direct main"
     description:

zxscanner/pubspec.yaml

@@ -15,7 +15,7 @@ dependencies:
     sdk: flutter
   flutter_localizations:
     sdk: flutter
-  flutter_markdown: ^0.6.12
+  flutter_markdown: ^0.6.13
   flutter_mobx: ^2.0.6
   flutter_zxing: ">=0.8.0 <1.0.0"
     # path: ../