Fix test workflow jest path

Uses regex, not glob (which would lead to Jest running all tests, not
only solution ones)

Author: mao-sz

.github/workflows/tests.yml

@@ -12,4 +12,4 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
       - run: npm install
-      - run: npm run test -- **/solution
+      - run: npm run test -- solution