Mnr typos in opaque.go

opaque.go

@@ -17,7 +17,7 @@
 package jose
 
 // OpaqueSigner is an interface that supports signing payloads with opaque
-// private key(s). Private key operations preformed by implementors may, for
+// private key(s). Private key operations performed by implementers may, for
 // example, occur in a hardware module. An OpaqueSigner may rotate signing keys
 // transparently to the user of this interface.
 type OpaqueSigner interface {