fixed xaxis label for updated SESANS nomenclature from z to delta #1871

Job	Run time
Generate test matrix	13s
Test (ubuntu-20.04, 3.11)	2m 52s
Test (ubuntu-20.04, 3.9)	2m 19s
Test (ubuntu-20.04, 3.10)	2m 2s
Test (windows-latest, 3.11)	5m 23s
Test (windows-latest, 3.9)	7m 27s
Test (windows-latest, 3.10)	8m 55s
Test (macos-latest, 3.11)	4m 12s
Test (macos-latest, 3.9)	4m 8s
Test (macos-latest, 3.10)	3m 54s
Test (ubuntu-latest, 3.11)	2m 50s
Test (ubuntu-latest, 3.9)	2m 12s
Test (ubuntu-latest, 3.10)	2m 22s
Installer (ubuntu-20.04, 3.11)	14m 2s
Installer (windows-latest, 3.11)	33m 32s
Installer (macos-latest, 3.11)	40m 44s
Test installer (windows-latest, 3.11)	2m 19s
Test installer (ubuntu-20.04, 3.11)	1m 38s
	2h 21m 4s

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