chore: Mark Cards component as a funnel substep

[connorlanigan]

Description

After this change, the Cards component is treated as a substep when it comes to funnel metrics, i.e. it is treated like a container.

Related links, issue #, if available: n/a

How has this been tested?

Extended the unit test

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (5f2f70c) 93.48% compared to head (8c3418b) 93.48%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1362   +/-   ##
=======================================
  Coverage   93.48%   93.48%           
=======================================
  Files         624      624           
  Lines       16797    16797           
  Branches     5549     5549           
=======================================
  Hits        15703    15703           
  Misses       1021     1021           
  Partials       73       73           

Impacted Files	Coverage Δ
src/cards/index.tsx	93.90% <100.00%> (ø)

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