fix(enterprise-teams): add ExactlyOneOf to data source and remove redundant ConflictsWith

[vmvarela]

Description

In data_source_github_enterprise_team, both team_slug and team_id have ConflictsWith set, but if ExactlyOneOf is used, ConflictsWith is redundant. Since we are removing team_id (#63), this issue covers ensuring the schema constraints are clean after that removal.

Acceptance Criteria

• After fix(enterprise-teams): remove team_id support — use only team_slug in all resources and data sources #63 is merged, confirm no redundant ConflictsWith remain alongside ExactlyOneOf or Required in any enterprise-teams schema
• Add top-level Description field to data_source_github_enterprise_team if missing
• Add top-level Description field to data_source_github_enterprise_team_membership if missing

Notes

Upstream PR: integrations#3008
Depends on: #63