Update dependency serverless-webpack to v5.15.3

Author: renovate[bot]

package.json

@@ -27,7 +27,7 @@
     "serverless-dotenv-plugin": "3.0.0",
     "serverless-dynamodb-local": "0.2.39",
     "serverless-offline": "6.8.0",
-    "serverless-webpack": "5.3.5",
+    "serverless-webpack": "5.15.3",
     "ts-loader": "8.0.7",
     "typescript": "3.9.5",
     "webpack": "4.44.2",