[Import]Fix #6461 MEASUREMENT/INSUNITS

[WandererFan]

This PR fixes issue #6461 where mm to inch calculation was performed twice for certain values of MEASUREMENT and INSUNITS variables in the imported DXF file.

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[freecadci]

for feature branch PR_6470. Pipeline 480439321 was triggered at 1102a55. All CI branches and pipelines.