chore: remove FluentAssertions ignore rule from dependabot.yml (#479)

* chore: remove FluentAssertions ignore rule from dependabot.yml

FluentAssertions was removed from the repo in #465/#476, so the
ignore rule pinning it to 5.10.3 is dead config.

* ci: re-trigger Windows validation (flake: GridFS snapshot 3s timeout)

Author: Aaronontheweb

.github/dependabot.yml

@@ -21,6 +21,3 @@ updates:
   - dependency-name: Akka.Persistence.Query
     versions:
     - 1.4.17
-  - dependency-name: FluentAssertions
-    versions:
-    - 5.10.3