gopls: move gopls/doc/generate package

This CL tracks adonovan's TODO by moving generate package from
gopls/doc/generate to gopls/internal/doc/generate.

Change-Id: I08fc90859cc6afe10ab5ac658a7b8a514d36cc32
Reviewed-on: https://go-review.googlesource.com/c/tools/+/654536
Reviewed-by: Alan Donovan <adonovan@google.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
Auto-Submit: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

Author: xieyuschen

gopls/internal/doc/api.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:generate go run ../../doc/generate
+//go:generate go run ./generate
 
 // The doc package provides JSON metadata that documents gopls' public
 // interfaces.

gopls/doc/generate/generate.go renamed to gopls/internal/doc/generate/generate.go

@@ -11,9 +11,7 @@
 //
 // Run it with this command:
 //
-//	$ cd gopls/internal/doc && go generate
-//
-// TODO(adonovan): move this package to gopls/internal/doc/generate.
+//	$ cd gopls/internal/doc/generate && go generate
 package main
 
 import (