Tracer-Web example npm start fails

[jonchurch]

To the best of my knowledge, a change introduced in #2225 added a line to the webpack config for the web-tracer example that broke the happy path for running the examples.

To reproduce:

cd examples/tracer-web

npm i && npm start

It attempts to bundle a file that doesn't exist, and as far as I can, tell has never existed in that dir.

I know that updating the examples in general is something that needs to be done, but I think it's important that what is already here works.

Single line PR incoming.

[dyladan]

Single line PR incoming 🚀