Pin npm version in CI

Author: kamils-iRonin

.github/workflows/ci.yml

@@ -18,7 +18,7 @@ jobs:
         with:
           node-version: ${{ matrix.node-version }}
       - name: Update npm to the latest version
-        run: npm install -g npm@latest
+        run: npm install -g npm@next-9
       - name: Install packages that are used in this pipeline
         run: npm install --global ajv-cli wait-on
       - run: npm install