Fix unmnemonic code coverage job (#60)

Author: backspace

.github/workflows/ci-unmnemonic-devices-vrs.yml

@@ -102,7 +102,7 @@ jobs:
           --locked
       - name: Generate code coverage
         working-directory: unmnemonic_devices_vrs
-        run: export $(cat .env.test | xargs) && cargo install [email protected] && cargo tarpaulin --verbose --workspace --out lcov --output-dir coverage
+        run: export $(cat .env.test | xargs) && cargo install [email protected] --locked && cargo tarpaulin --verbose --workspace --out lcov --output-dir coverage
         env:
           DATABASE_URL: postgres://postgres:postgres@localhost/postgres
       - name: Coveralls GitHub Action