cli/registry/client: remove dependency on trust / notary

[thaJeztah]

• follow-up to Assorted cleanups to reduce trust / notary imports #5878

The client was only using the Actions consts, but the trust package also has a dependency on notary. Remove the import to prevent Notary becoming a dependency for uses of the cli code.

- A picture of a cute animal (not mandatory but encouraged)

[thaJeztah]

Looks like I forgot to include this one in #5878 - this one should also be trivial; the predefined vars are nice, but don't add much value, and we shouldn't depend on the trust code for this (more likely it should've been the other way round)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 59.31%. Comparing base (076ec3b) to head (e3da0cc).
Report is 2 commits behind head on master.

Additional details and impacted files

@@ Coverage Diff @@## master #5880 +/- ##
=======================================
Coverage 59.31% 59.31% =======================================
Files 353 353 Lines 29735 29735 =======================================
Hits 17637 17637 Misses 11117 11117 Partials 981 981