Updated replacetokens-task from v3 to v6

[ollief87]

Updated qetza/replacetokens-task from v3 to v6 based on below guidance:

• https://github.com/qetza/replacetokens-task/discussions/33
• https://github.com/qetza/replacetokens-task/discussions/34

Fixes issue https://github.com/Azure/apiops/issues/675