node: missing comma on toml tags (#21187)

Author: mcortesi

node/config.go

@@ -83,7 +83,7 @@ type Config struct {
 	KeyStoreDir string `toml:",omitempty"`
 
 	// ExternalSigner specifies an external URI for a clef-type signer
-	ExternalSigner string `toml:"omitempty"`
+	ExternalSigner string `toml:",omitempty"`
 
 	// UseLightweightKDF lowers the memory and CPU requirements of the key store
 	// scrypt KDF at the expense of security.