Fix test for matmul with abstract block types

[mtfishman]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.97%. Comparing base (d55caaa) to head (7f4384a).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #151   +/-   ##
=======================================
  Coverage   73.97%   73.97%           
=======================================
  Files          36       36           
  Lines        1875     1875           
=======================================
  Hits         1387     1387           
  Misses        488      488           

Flag	Coverage Δ
docs	7.80% <ø> (ø)

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