remove extra pressure scale in scale_flux for 1d cartesian

[zhichen3]

PR summary

addresses #2803 . In #2468, we modified mom_flux_has_p to include pressure in momentum flux with 1d cartesian, so we don't need to scale pressure again scale_flux.

PR motivation

PR checklist

• test suite needs to be run on this PR
• this PR will change answers in the test suite to more than roundoff level
• all newly-added functions have docstrings as per the coding conventions
• the CHANGES file has been updated, if appropriate
• if appropriate, this change is described in the docs

[zingale]

tests: http://groot.astro.sunysb.edu/Castro/test-suite/gfortran/2024-11-12-001/index.html