Don't include `example_pipeline` in pyproject.toml

[deepyaman]

Motivation and Context

Causes issues for users: https://kedro-org.slack.com/archives/C03RKP2LW64/p1704764421756699

Can be reverted when next Kedro version is released, or ProjectMetadata is made more flexible.

How has this been tested?

Blind faith

Checklist

• [x] Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• [ ] Assigned myself to the PR
• [ ] Added tests to cover my changes

[SajidAlamQB]

The long term solution to avoid this happening in the future is here: https://github.com/kedro-org/kedro/pull/3504

This won't fix this problem until we do the next release so we might need to merge this PR for now until then.

[SajidAlamQB]

Closing in favour of https://github.com/kedro-org/kedro/pull/3504, we will do a release to get this in ASAP.