doc: Clarifies private endpoint resource docs

[zach-carr]

Description

The resources mongodbatlas_privatelink_endpoint_service and mongodbatlas_privatelink_endpoint map to contradictory terminology -- privatelink_endpoint_service affects Private Endpoints, and privatelink_endpoint affects Private Endpoint Services. To help clarify, I've added links to a new section of the Atlas documentation that defines these terms as MongoDB uses them.

Link to any related issue(s):

Type of change:

• Bug fix (non-breaking change which fixes an issue). Please, add the "bug" label to the PR.
• New feature (non-breaking change which adds functionality). Please, add the "enhancement" label to the PR.
• Breaking change (fix or feature that would cause existing functionality to not work as expected). Please, add the "breaking change" label to the PR.
• This change requires a documentation update
• Documentation fix/enhancement

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• I have signed the MongoDB CLA
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• I have added tests that prove my fix is effective or that my feature works per HashiCorp requirements
• I have added any necessary documentation (if appropriate)
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Further comments

[zach-carr]

unrelated fix to note rendering

[sarahsimpers]

LGTM, thank you!

[oarbusi]

Thanks! LGTM