Bump flutter_markdown in /experimental/linting_tool (#1099)

Bumps [flutter_markdown](https://github.com/flutter/packages) from 0.6.9+1 to 0.6.10.
- [Release notes](https://github.com/flutter/packages/releases)
- [Commits](https://github.com/flutter/packages/compare/flutter_markdown-v0.6.9...flutter_markdown-v0.6.10)

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

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

experimental/linting_tool/pubspec.lock

@@ -278,7 +278,7 @@ packages:
       name: flutter_markdown
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.6.9+1"
+    version: "0.6.10"
   flutter_test:
     dependency: "direct dev"
     description: flutter
@@ -414,7 +414,7 @@ packages:
       name: markdown
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "4.0.1"
+    version: "5.0.0"
   matcher:
     dependency: transitive
     description: