Cleanup the internal lakeflow-pipelines template (#3656)

## Changes
This cleans up the internal `lakeflow-pipelines` template, removing an
unused file and excluding the unused `lib/` folder.

## Why
* The `lakeflow-pipelines` template doesn't currently make use of a
Python package, since the "Include a Python package?" question defaults
to "no."
* The `lakeflow-pipelines` template currently still doesn't make use of
an environment and the `lib/` folder. That is expected to be added in an
upcoming version.

## Testing
* Manual testing + updated acceptance tests

Author: lennartkats-db

acceptance/bundle/templates/lakeflow-pipelines/python/output/my_lakeflow_pipelines/lib/shared/__init__.py

@@ -55,6 +55,7 @@ This file only template directives; it is skipped for the actual output.
 {{if $lakeflow_only}}
   # Only include a simple job.yml direcly in resources/{{.project_name_short}}_etl
   {{skip "{{.project_name}}/resources/sample_job/**"}}
+  {{skip "{{.project_name}}/lib/**"}}
 {{else}}
   # Include a full job that might have more than one task
   {{skip "{{.project_name}}/resources/{{.project_name_short}}_etl/*.job.yml"}}