Fix a small bug in the way gate types in specs are accumulated

[Qottmann]

Context:
Fix a small bug in the way gate types in specs are accumulated

Test is co-written by yours truly, Jukebox (Claude)

Description of the Change:

Small fix so same gate types don't get overwritten

Benefits:

Fixes bug

Possible Drawbacks:

Related GitHub Issues:

[github-actions]

Hello. You may have forgotten to update the changelog!
Please edit doc/releases/changelog-dev.md with:

• A one-to-two sentence description of the change. You may include a small working example for new features.
• A link back to this PR.
• Your name (or GitHub username) in the contributors section.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.45%. Comparing base (2e795d5) to head (e78e285).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9574   +/-   ##
=======================================
  Coverage   99.44%   99.45%           
=======================================
  Files         614      614           
  Lines       67863    67863           
=======================================
+ Hits        67489    67490    +1     
+ Misses        374      373    -1     

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[JerryChen97]

Ahhhhh I actually can't believe this didn't cause any catastrophic cascading problems in our tests 😓