The arguments of nova CLI commands related to host aggregate
(I93f44a12b6d5a91b448f6f8d238311d58bf40c01) are fixed.
The host APIs have been deprecated since microversion 2.43.
So remove description related to nova host commands.
And add description about nova hypervisor commands.
Change-Id: Ibf78865844da6f007b610f12430df4866076f00b
Closes-Bug: #1726658