Docs: Update media_share_idracs code block

[christophermay07]

From Install.md: "

#media_share_idracs:
#  - name: master-0
#    ip: '{{ ip_space }}.5'
#  - name: master-1
#    ip: '{{ ip_space }}.6'
#  - name: master-2
#    ip: '{{ ip_space }}.7'
#  - name: worker-0
#    ip: '{{ ip_space }}.8'

"

Redline text #1: "unless ip_space is built somewhere" (sic) Redline text #2: "Only need 3 blocks max, drop one (there are no 4 node setups in field)"

Find out what the first redline comment is supposed to be, and address the comment about the 4 node setup.