Update ManualClusterSetup.md
Update ManualClusterSetup.md

Updated introductory paragraph.

Former-commit-id: 176aff6fd9363224c64323873c84a874bae294d1
alexhersh/libcalico,insequent/libcalico,TrimBiggs/libnetwork-plugin,TrimBiggs/libnetwork-plugin,djosborne/libcalico,robbrockbank/libcalico,tomdee/libcalico,projectcalico/libcalico,caseydavenport/libcalico,projectcalico/libnetwork-plugin,TrimBiggs/libcalico,Symmetric/libcalico,tomdee/libnetwork-plugin,L-MA/libcalico,plwhite/libcalico