TrigP1Test: Fix for magFieldToggle ART test

Two fixes for the magFieldToggle ART test (ATR-21978):

• Update reference for field off run. This is due to !36073 (merged), which introduced a fix for the case of zero field.
• Fix for Python2 build.

This merge request affects 1 package:

• Trigger/TrigValidation/TrigP1Test

Adding @okumura ,@salderwe ,@jpanduro as watchers

added Trigger master review-pending-level-1 labels

CI Result SUCCESS (hash 839f90b9)

	Athena	AthSimulation	AthGeneration	AnalysisBase
externals
cmake
make
required tests
optional tests

Full details available on this CI monitor view
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
AthGeneration: number of compilation errors 0, warnings 0
AnalysisBase: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 20066]

Looks good, approving --L1

added review-pending-level-2 label and removed review-pending-level-1 label

added review-approved label and removed review-pending-level-2 label

merged

mentioned in commit 3d72e0f6

added sweep:ignore label