Fix warning message from get_all_items deprecation

[gadomski]

Related Issue(s):

• Introduced in Expand get_items - deprecate get_all_items and Catalog.get_item  #1075

Description:

Also, remove usages of deprecated functions.

PR Checklist:

• pre-commit hooks pass locally
• 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]

Codecov Report

Patch and project coverage have no change.

Comparison is base (00612b3) 92.01% compared to head (98d511f) 92.01%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1203   +/-   ##
=======================================
  Coverage   92.01%   92.01%           
=======================================
  Files          51       51           
  Lines        6813     6813           
  Branches     1009     1009           
=======================================
  Hits         6269     6269           
  Misses        368      368           
  Partials      176      176           

Files Changed	Coverage Δ
pystac/catalog.py	93.37% <ø> (ø)

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.