Fix CI/CD example. Single quote does not expand variables

doc/user/packages/npm_registry/index.md

@@ -308,7 +308,7 @@ stages:
 deploy:
   stage: deploy
   script:
-    - echo '//gitlab.com/api/v4/projects/${CI_PROJECT_ID}/packages/npm/:_authToken=${CI_JOB_TOKEN}'>.npmrc
+    - echo "//gitlab.com/api/v4/projects/${CI_PROJECT_ID}/packages/npm/:_authToken=${CI_JOB_TOKEN}">.npmrc
     - npm publish
 ```