Example for Generating Protos Using the scripts seems broken

Hey Team,

I am trying to use the repo and scripts to generate protos from my custom Implementation guide.

I am trying to follow the guidelines mentioned in this link: https://github.com/google/fhir-examples/blob/master/USERGUIDE.md#generating-protos-from-profiles

As an example I am trying to use the "US Core protos:" example., which seem to be failing for bullet points: 3(link is broken) and 4 with the following error (this was updating the command to: generate_protos.sh //proto/google/fhir/proto/r4:uscore)

```guptarju@guptarju:~/google-fhir/fhir$ generate_protos.sh //proto/google/fhir/proto/r4:uscore
ERROR: Skipping 'proto/google/fhir/proto/r4:uscore_proto_files': no such target '//proto/google/fhir/proto/r4:uscore_proto_files': target 'uscore_proto_files' not declared in package 'proto/google/fhir/proto/r4' (did you mean 'uscore_proto_zip'?) defined by /usr/local/google/home/guptarju/google-fhir/fhir/proto/google/fhir/proto/r4/BUILD
WARNING: Target pattern parsing failed.
ERROR: no such target '//proto/google/fhir/proto/r4:uscore_proto_files': target 'uscore_proto_files' not declared in package 'proto/google/fhir/proto/r4' (did you mean 'uscore_proto_zip'?) defined by /usr/local/google/home/guptarju/google-fhir/fhir/proto/google/fhir/proto/r4/BUILD
INFO: Elapsed time: 0.220s
INFO: 0 processes.
FAILED: Build did NOT complete successfully (0 packages loaded)
Build Failed: proto/google/fhir/proto/r4:uscore_proto_files```

Is there any update guide? Which could be referenced or the content within this file be updated