Reference 6.1 for key changeover (#249)

RFC 3647 says that the key changeover section "describes the procedures
to provide a new public key to a CA's users following a re-key by the
CA. These procedures may be the same as the procedure for providing the
current key."

Since section 6.1 describes the procedures for generating and providing
the current CA keys to relying parties, it is a better reference than
section 2.2.

CP-CPS.md

@@ -772,7 +772,7 @@ No stipulation.
 
 ## 5.6 Key changeover
 
-See Section 2.2.
+See Section 6.1.
 
 ## 5.7 Compromise and disaster recovery