build(deps): bump file from 6.1.4 to 7.0.0

Bumps [file](https://github.com/google/file.dart/tree/master/packages) from 6.1.4 to 7.0.0.
- [Release notes](https://github.com/google/file.dart/releases)
- [Commits](https://github.com/google/file.dart/commits/v7.0.0/packages)

---
updated-dependencies:
- dependency-name: file
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

pubspec.yaml

@@ -33,7 +33,7 @@ dependencies:
 
 dev_dependencies:
   coverage: ">=0.15.0 <2.0.0"
-  file: ^6.1.1
+  file: ">=6.1.1 <8.0.0"
   import_sorter: ^4.6.0
   lints: ^3.0.0
   test: ^1.15.7