remove postgres-specific reference to `pg_views.relkind='m'`

[dataders]

Description

resolves: #173

Motivation and Context

Testing

Screenshots (if appropriate)

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)

Checklist

• [ ] Local run of ./build.sh succeeds
• [ ] Code changes have been run against the repository's pre-commit hooks
• [ ] Commit messages follow Conventional Commit Specification
• [ ] I have read the README document
• [ ] I have added tests to cover my changes
• [ ] I have run all unit tests using pytest test/unit and they are passing.

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