A vulnerability scan listed SNMPv2c and we've been asked to disable it.
How can we do so and what, if any, impact would this have if we're not monitoring the DRACs via SNMP.
You can either disable SNMP or enable only SNMP v3 on iDRAC. You can change this setting from below page of iDRAC GUI
Overview -> iDRAC Settings -> Network -> Services
Refer SNMP Agent section for SNMP related changes
If you are not doing any monitoring of iDRAC using SNMP, changing SNMP setting will not impact your iDRAC.