Incorrect collection name in multiple versions of the documentation

[YHatahet]

Similar to this issue but on the Charmed MongoDB K8s documentation.

Under multiple versions, in the "Relate your MongoDB deployment" section, "test-collection" with a hyphen is being referred to as "test_collection" with an underscore.

[github-actions]

https://warthogs.atlassian.net/browse/DPE-3208