tests: Trust method signature to be accurate

[l0b0]

Catalog.get_all_items is contracted to return Iterable[Item], so we
shouldn't have to filter the response.

Related Issue(s): #331

Description:

PR Checklist:

• Code is formatted (run pre-commit run --all-files)
• Tests pass (run scripts/test)
• Documentation has been updated to reflect changes, if applicable
• This PR maintains or improves overall codebase code coverage.
• Changes are added to the CHANGELOG. See the docs for information about adding to the changelog.

[codecov-commenter]

Codecov Report

Merging #516 (833e990) into main (a4fe4cd) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #516      +/-   ##
==========================================
+ Coverage   93.96%   93.97%   +0.01%     
==========================================
  Files          71       71              
  Lines        9991     9991              
  Branches     1061     1060       -1     
==========================================
+ Hits         9388     9389       +1     
  Misses        434      434              
+ Partials      169      168       -1     

Impacted Files	Coverage Δ
tests/test_item.py	100.00% <100.00%> (+0.21%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a4fe4cd...833e990. Read the comment docs.