Rename the query constant to have an underscore in it. (#241)

We got reports of conflicts with the old constant-name and symbols that
people were defining in their app.

generate/testdata/snapshots/TestGenerate-InterfaceListField.graphql-InterfaceListField.graphql.go

@@ -521,7 +521,7 @@ func (v *InterfaceListFieldWithPointerTopicChildrenVideo) GetId() testutil.ID {
 func (v *InterfaceListFieldWithPointerTopicChildrenVideo) GetName() string { return v.Name }
 
 // The query or mutation executed by InterfaceListField.
-const InterfaceListFieldOperation = `
+const InterfaceListField_Operation = `
 query InterfaceListField {
 	root {
 		id
@@ -549,7 +549,7 @@ func InterfaceListField(
 ) (*InterfaceListFieldResponse, error) {
 	req := &graphql.Request{
 		OpName: "InterfaceListField",
-		Query:  InterfaceListFieldOperation,
+		Query:  InterfaceListField_Operation,
 	}
 	var err error