Update X-Trino-Role in client request headers table

[sheajamba]

Description

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Fix

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Documentation

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Fix link syntax to CREATE ROLE page. Previously did not link to anything.

Related issues, pull requests, and links

Documentation

( ) No documentation is needed.
(x) Sufficient documentation is included in this PR.
( ) Documentation PR is available with #prnumber.
( ) Documentation issue #issuenumber is filed, and can be handled later.

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# Section
* Fix some things. ({issue}`issuenumber`)

[mosabua]

Thanks for the quick fix.

[ebyhr]

Merged, thanks!