test: replace jest-mock with sinon, drop expect

Author: gjf7

.github/dependabot.yml

@@ -33,9 +33,9 @@ updates:
               patterns:
                   - 'mocha*'
                   - '@types/mocha'
-                  - 'jest*'
+                  - '@types/sinon'
+                  - 'sinon'
                   - 'c8'
-                  - 'expect'
     # Check for updates to GitHub Actions every week
     - package-ecosystem: 'github-actions'
       directory: '/'