added reference to audit subproject and kubernetes-sigs repo

Author: aasmall

sig-security/security-audit-2021/RFP.md

@@ -2,7 +2,7 @@
 
 ## Kubernetes Third-Party Security Audit
 
-The Kubernetes Third-Party Audit Working Group (working group, henceforth) is soliciting proposals from Information Security vendors for a comprehensive security audit of the Kubernetes Project.
+The Kubernetes SIG Security Third-Party Audit sub-project (working group, henceforth) is soliciting proposals from Information Security vendors for a comprehensive security audit of the Kubernetes Project.
 
 ### Background
 
@@ -19,7 +19,7 @@ These findings, below, paint a broad picture of Kubernetes security, as of versi
 
 This subsequent audit is intended to be the second in a series of recurring audits, each focusing on a specific aspect of Kubernetes while maintaining coverage of all aspects that have changed since the previous audit ([1.13](../security-audit-2019/findings/)).
 
-The scope of this audit is the most recent release (1.20) of the core [Kubernetes project](https://github.com/kubernetes/kubernetes).
+The scope of this audit is the most recent release (1.20) of the core [Kubernetes project](https://github.com/kubernetes/kubernetes) and certain other code maintained by [Kubernetes SIGs](https://github.com/kubernetes-sigs/).
 
 This audit will focus on the following components of Kubernetes: