chore(deps): pin dependencies (#107)

Author: renovate[bot]

package.json

@@ -23,7 +23,7 @@
   "devDependencies": {
     "@nestjs/common": "6.8.2",
     "@nestjs/core": "6.8.2",
-    "@nestjs/platform-express": "^6.8.2",
+    "@nestjs/platform-express": "6.8.2",
     "@nestjs/testing": "6.8.2",
     "@semantic-release/changelog": "3.0.4",
     "@types/jest": "24.0.18",
@@ -34,7 +34,7 @@
     "rxjs": "6.5.3",
     "rxjs-marbles": "5.0.3",
     "semantic-release": "15.13.24",
-    "supertest": "^4.0.2",
+    "supertest": "4.0.2",
     "ts-jest": "24.1.0",
     "tsc-watch": "4.0.0",
     "tslint": "5.20.0"