Update function name for system instruction

Author: kinarr

go/system_instruction.go

@@ -9,7 +9,7 @@ import (
 )
 
 // SystemInstructions demonstrates setting a system instruction using a *genai.Content in the generation config.
-func SystemInstructions() error {
+func SystemInstruction() error {
 	// [START system_instruction]
 	ctx := context.Background()
 	client, err := genai.NewClient(ctx, &genai.ClientConfig{

go/system_instruction_test.go

@@ -4,9 +4,9 @@ import (
 	"testing"
 )
 
-func TestSystemInstructions(t *testing.T) {
-	err := SystemInstructions()
+func TestSystemInstruction(t *testing.T) {
+	err := SystemInstruction()
 	if err != nil {
-		t.Errorf("SystemInstructions returned an error.")
+		t.Errorf("SystemInstruction returned an error.")
 	}
 }