Replace dependency apollo-server-core with @apollo/server ^4.0.0

Author: renovate[bot]

package.json

@@ -9,7 +9,7 @@
     "@cloudnative/health": "^2.1.2",
     "@graphql-tools/schema": "^8.3.3",
     "@koa/router": "^10.1.1",
-    "apollo-server-core": "^3.6.4",
+    "@apollo/server": "^4.0.0",
     "apollo-server-koa": "^3.6.4",
     "bluebird": "^3.7.2",
     "bunyan": "^1.8.15",