Bugfix for _replace_units

[samwaseda]

Closes #2111

I encountered the following bug:

This one works:

def f(C, x, P):
    return np.linalg.norm(P) / np.linalg.norm(C) / x**2

f(np.random.randn(2, 3, 4), np.random.randn(5, 6), np.random.randn(7, 8))

This one doesn't:

@ureg.wraps("=P/C/x**2", ("=C", "=x", "=P"))
def f(C, x, P):
    return np.linalg.norm(P) / np.linalg.norm(C) / x**2

f(np.random.randn(2, 3, 4) * ureg.gigapascal, np.random.randn(5, 6) * ureg.meter, np.random.randn(7, 8) * ureg.joule)

The fix I'm proposing here would solve the problem.

• Closes # (insert issue number)
• Executed pre-commit run --all-files with no errors
• The change is fully covered by automated unit tests
• Documented in docs/ as appropriate
• Added an entry to the CHANGES file

[codspeed-hq]

CodSpeed Performance Report

Merging #2110 will not alter performance

_{Comparing samwaseda:patch-1 (73a51f0) with master (74b7086)}

Summary

✅ 437 untouched benchmarks