Install Nextest correctly during CI

Author: Aaron Fenyes

.github/workflows/ci.yml

@@ -41,7 +41,9 @@ jobs:
                   override: true
             - uses: Swatinem/rust-cache@v2
             - name: Install test dependencies
-              run: cargo install cargo-nextest cargo-expand
+              run: |
+                  cargo install cargo-nextest --locked
+                  cargo install cargo-expand
             - name: Run tests
               run: cargo nextest run
             - name: Run documentation tests