sql: fix outdated evalgen instructions

Release note: None

Author: mgartner

pkg/sql/sem/tree/eval_expr_generated.go

@@ -6,10 +6,9 @@
 // Command evalgen is used to generate interfaces and "visitor" methods for
 // expr and op evaluation.
 //
-// Generated files can be regenerated with either of the follow commands:
+// Generated files can be regenerated with the command:
 //
 //	./dev generate go
-//	go generate ./pkg/sql/sem/tree
 package main
 
 import (
@@ -94,10 +93,9 @@ const header = `// Copyright 2022 The Cockroach Authors.
 // included in the /LICENSE file.
 
 // Code generated by eval_gen.go. DO NOT EDIT.
-// Regenerate this file with either of the following commands:
+// Regenerate this file with the command:
 //
 //   ./dev generate go
-//   go generate ./pkg/sql/sem/tree
 //
 // If you use the dev command and you have added a new tree expression, like
 // tree.XYZ in a new file, you may get the confusing error: undefined: XYZ.