Fix and test for misinterpreted dimensionless power of exponent

[blackyblack]

References to other Issues or PRs

Fixes #24062

Brief description of what is fixed or changed

Added test for this issue in sympy/physics/units/tests/test_quantities.py
In _collect_factor_and_dimension() added additional check if expression is dimensionless.

Other comments

Release Notes

• physics.units
  • Fixed a bug with dimensionless power of exponent

[sympy-bot]

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• physics.units
  • Fixed a bug with dimensionless power of exponent (#24066 by @blackyblack)

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<!-- Your title above should be a short description of what
was changed. Do not include the issue number in the title. -->

#### References to other Issues or PRs
Fixes #24062


#### Brief description of what is fixed or changed
Added test for this issue in sympy/physics/units/tests/test_quantities.py
In _collect_factor_and_dimension() added additional check if expression is dimensionless.


#### Other comments


#### Release Notes

<!-- BEGIN RELEASE NOTES -->

* physics.units
  * Fixed a bug with dimensionless power of exponent

<!-- END RELEASE NOTES -->

Update

The release notes on the wiki have been updated.

[oscarbenjamin]

You'll need to add yourself to .mailmap as mentioned in the failed authors test.

[github-actions]

Benchmark results from GitHub Actions

Lower numbers are good, higher numbers are bad. A ratio less than 1
means a speed up and greater than 1 means a slowdown. Green lines
beginning with + are slowdowns (the PR is slower then master or
master is slower than the previous release). Red lines beginning
with - are speedups.

Significantly changed benchmark results (PR vs master)

Significantly changed benchmark results (master vs previous release)

       before           after         ratio
     [41d90958]       [514579c6]
     <sympy-1.11.1^0>                 
-     1.36±0.04ms         877±40μs     0.65  solve.TimeSparseSystem.time_linear_eq_to_matrix(10)
-      3.96±0.2ms      1.62±0.04ms     0.41  solve.TimeSparseSystem.time_linear_eq_to_matrix(20)
-      7.75±0.2ms      2.43±0.05ms     0.31  solve.TimeSparseSystem.time_linear_eq_to_matrix(30)

Full benchmark results can be found as artifacts in GitHub Actions
(click on checks at the top of the PR).

[oscargus]

Thanks!