Remove default value for prefix input in "monolith" Quickstart OCP DA

[ocofaigh]

Prefix should not have a default value (it defeats the point of prefix which is to prevent name clashes):

terraform-ibm-landing-zone/patterns/roks-quickstart/variables.tf

Line 14 in 4d3805f

default = "lz-roks-qs"

[piyush117]

PR merged, hence closing.