[NEAT-211] Move is_reference from importers to Excel Importer

[doctrino]

No description provided.

[github-actions]

☂️ Python Coverage

current status: ✅

Overall Coverage

Lines	Covered	Coverage	Threshold	Status
18766	12500	67%	60%	🟢

New Files

No new covered files...

Modified Files

File	Coverage	Status
cognite/neat/rules/exporters/_rules2excel.py	83%	🟢
cognite/neat/rules/importers/_base.py	85%	🟢
cognite/neat/rules/importers/_dms2rules.py	83%	🟢
cognite/neat/rules/importers/_dtdl2rules/dtdl_importer.py	73%	🟢
cognite/neat/rules/importers/_owl2rules/_owl2rules.py	92%	🟢
cognite/neat/rules/importers/_spreadsheet2rules.py	72%	🟢
cognite/neat/rules/importers/_yaml2rules.py	64%	🟢
cognite/neat/rules/models/rules/_dms_architect_rules.py	91%	🟢
cognite/neat/rules/models/rules/_domain_rules.py	98%	🟢
cognite/neat/rules/models/rules/_information_rules.py	89%	🟢
cognite/neat/workflows/steps/lib/rules_importer.py	30%	🟢
TOTAL	78%	🟢

updated for commit: e3845b0 by action🐍