refactor: removed 1.12.0 deprecated fields.

[marcosuma]

Description

Removing all the fields that have been declared as to be deprecated in v1.12.0.

Link to any related issue(s): https://jira.mongodb.org/browse/INTMDB-1015

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

Required Checklist:

• I have signed the MongoDB CLA
• I have read the contribution guidelines
• 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)
• I have run make fmt and formatted my code

Further comments

[andreaangiolillo]

Make sure to update the documentation as well: https://github.com/mongodb/terraform-provider-mongodbatlas/tree/master/website/docs

r = resources and d = data sources

[andreaangiolillo]

changes LGTM after reverting the removed acceptance tests.

Great work here 💯 !

One last action to do as part of this ticket is to add a list of deprecated fields per resource/datasource in the PR description (or in the JIRA ticket) to help us add this info in the CHANGELOG before the release.

[AgustinBettati]

LGTM, thanks for addressing the test change. Would look into Andreas last comment before merging.