Clarify SSO permissions mapping docs

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 38.42%. Comparing base (bf28589) to head (7bf70de). Report is 15 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #4107 +/- ## ========================================== - Coverage 38.44% 38.42% -0.03% ========================================== Files 723 724 +1 Lines 33247 33274 +27 Branches 4889 4725 -164 ========================================== + Hits 12783 12785 +2 - Misses 19315 19865 +550 + Partials 1149 624 -525 ``` | [Flag](https://app.codecov.io/gh/quiltdata/quilt/pull/4107/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=quiltdata) | Coverage Δ | | |---|---|---| | [api-python](https://app.codecov.io/gh/quiltdata/quilt/pull/4107/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=quiltdata) | `90.85% <ø> (ø)` | | | [catalog](https://app.codecov.io/gh/quiltdata/quilt/pull/4107/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=quiltdata) | `11.43% <ø> (-0.01%)` | :arrow_down: | | [lambda](https://app.codecov.io/gh/quiltdata/quilt/pull/4107/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=quiltdata) | `87.95% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=quiltdata#carryforward-flags-in-the-pull-request-comment) to find out more.

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