Update version number to 1.6 (#135) #27

Job	Run time
build_test (3.14, nequip)	2m 3s
build_test (3.14, fennix)	3m 41s
build_test (3.12, orb)	8m 59s
build_test (3.14, mace-aimnet-torchmd)	9m 48s
	24m 31s

Provide feedback