chore: update copyright text 2023

[paulocfjunior]

What does this PR do?

Changes the Copyright text in the documentation.

How to test it

• Navigate to the /docs directory
• Run make serve
• Check the documentation at http://0.0.0.0:8000/traefik-mesh/

Additional Notes

• The year of the copyright is already set for 2023

[CLAassistant]

All committers have signed the CLA.