Add UPDATE to file-based access control docs

[nineinchnick]

Description

Add UPDATE to file-based access control docs, required by UPDATE <table> but also REFRESH MATERIALIZED VIEW

Is this change a fix, improvement, new feature, refactoring, or other?
update existing docs

Is this a change to the core query engine, a connector, client library, or the SPI interfaces? (be specific)
docs

How would you describe this change to a non-technical end user or system administrator?
document missing permission

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.

Release notes

(x) No release notes entries required.
( ) Release notes entries required with the following suggested text:

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

[kokosing]

Merged, thanks!