docs(aws-serverless): Add comment about dist path import (#12383)

Adding a comment in `package.json` with `"//"` is safe, as npm reserved
this for comments ([see
here](https://groups.google.com/g/nodejs/c/NmL7jdeuw0M/m/yTqI05DRQrIJ)).

---------

Co-authored-by: Francesco Novy <francesco.novy@sentry.io>

packages/aws-serverless/package.json

@@ -47,6 +47,7 @@
       }
     },
     "./dist/awslambda-auto": {
+      "//": "@deprecated Use `./awslambda-auto` instead",
       "require": {
         "default": "./build/npm/cjs/awslambda-auto.js"
       }