Switches to NXscan for eln test

[domna]

The eln test should not depend on the NXmpes definition as this may change.
I switched it to NXscan as this is a definition which is already contributed and will likely not change in the coming months.

[coveralls]

Pull Request Test Coverage Report for Build 7976397026

Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• 12 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-0.02%) to 44.561%

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Files with Coverage Reduction	New Missed Lines	%
pynxtools/dataconverter/readers/shared/map_concepts/mapping_functors.py	1	11.86%
pynxtools/nexus/nxdl_utils.py	2	74.95%
pynxtools/eln_mapper/scheme_eln.py	3	89.72%
pynxtools/eln_mapper/eln.py	6	79.45%

Totals
Change from base Build 7961488576:	-0.02%
Covered Lines:	4903
Relevant Lines:	11003

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💛 - Coveralls

[RubelMozumder]

This is just the chnage of the file to be subject in this tool and the change in the corresponding reference to the file. Everything looks fine