remove some assertXxx funcs

keys/cryptostore/holder.go

@@ -24,19 +24,10 @@ func New(coder Encoder, store keys.Storage, codec keys.Codec) Manager {
 	}
 }
 
+// assert Manager satisfies keys.Signer and keys.Manager interfaces
 var _ keys.Signer = Manager{}
 var _ keys.Manager = Manager{}
 
-// exists just to make sure we fulfill the Signer interface
-func (s Manager) assertSigner() keys.Signer {
-	return s
-}
-
-// exists just to make sure we fulfill the Manager interface
-func (s Manager) assertKeyManager() keys.Manager {
-	return s
-}
-
 // Create adds a new key to the storage engine, returning error if
 // another key already stored under this name
 //