[recommendation] rename recommendationservice to recommendation

[puckpuck]

Changes

Renames recommendationservice to recommendation

This is part of getting all services renamed based on the overall #1788 effort for all components in the demo.

Merge Requirements

For new features contributions, please make sure you have completed the following
essential items:

• CHANGELOG.md updated to document new feature additions
• Appropriate documentation updates in the docs
• Appropriate Helm chart updates in the helm-charts

Maintainers will not merge until the above have been completed. If you're unsure
which docs need to be changed ping the
@open-telemetry/demo-approvers.

[mviitane]

LGTM. Runs fine.