use backstage version in backend plugin scaffold

packages/cli/templates/default-backend-plugin/package.json.hbs

@@ -23,8 +23,8 @@
       "clean": "backstage-cli clean"
     },
     "dependencies": {
-      "@backstage/backend-common": "^{{version}}",
-      "@backstage/config": "^{{version}}",
+      "@backstage/backend-common": "^{{backstageVersion}}",
+      "@backstage/config": "^{{backstageVersion}}",
       "@types/express": "^4.17.6",
       "express": "^4.17.1",
       "express-promise-router": "^3.0.3",
@@ -33,7 +33,7 @@
       "yn": "^4.0.0"
     },
     "devDependencies": {
-      "@backstage/cli": "^{{version}}",
+      "@backstage/cli": "^{{backstageVersion}}",
       "@types/supertest": "^2.0.8",
       "supertest": "^4.0.2",
       "msw": "^0.20.5"