Self-managed node group example testing and updates

[naris-silpakit]

What does this PR do?

Updates the example so it only creates 3 public and 3 private subnets as described in the readme. This PR also serves to validate that this example still works. This PR also includes a small whitespace fix that was caught by pre-commit.

More

• Yes, I have tested the PR using my local account setup (Provide any test evidence report under Additional Notes)
• Yes, I have added a new example under examples to support my PR
• Yes, I have created another PR for add-ons under add-ons repo (if applicable)
• Yes, I have updated the docs for this feature
• Yes, I ran pre-commit run -a with this PR

Note: Not all the PRs required examples and docs except a new pattern or add-on added.

For Moderators

• E2E Test successfully complete before merge?

Additional Notes

Followed the readme deployment and testing steps to validate that it works as expected.

[naris-silpakit]

Whoops, I forgot to make some of the other updates for this example. Closing for now and will open a new PR once I fix this.

[naris-silpakit]

Double-checked that everything was correct - PR ready for review.

[kcoleman731]

LGTM