prospective changes from WGLC reviews (#171)

* Attempt to slightly reword the last sentence in sec 2 for readability and not mentioning client auth part of 7523 here

* Mention that the RFC8693 token exchange is not strictly nessessary, if trust domain A's platform provides other means to obtain a JWT authorization grant

* Consistently just a single horizontal space between items in the swim lanes

* Better describe the trust relationship necessary (domain B has to trusts domain A to issue JWT authz grants and trust its signing key(s)) and mention that AS Metadata's `jwks_uri` can be used to obtain the verification keys for trust domain A (fixes #169)

* typo belows

* editorial fixes

* add a note about agreeing on semantics etc. when transcribing claims (for #170 per Watson Ladd with hopefully wording more consistent with the the rest of the text)

* qualify what aud prevents a bit

* don't think audience is the right word there

* that's data minimization more than selective disclosure me thinks

* Just one hyphen in SSO

* back to the big D

* Update draft-ietf-oauth-identity-chaining.md

Co-authored-by: Aaron Parecki <aaron@parecki.com>

* little

* Update draft-ietf-oauth-identity-chaining.md

Co-authored-by: PieterKas <90690777+PieterKas@users.noreply.github.com>

* one less line

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Co-authored-by: Aaron Parecki <aaron@parecki.com>
Co-authored-by: PieterKas <90690777+PieterKas@users.noreply.github.com>

Author: 3 people