cmd/go: remove stray reference to mkalldocs.sh

Clean up a stray reference in the docs to 'mkalldocs.sh', which no
longer exists (was replaced by a Go program, in 676794f73e).

Change-Id: I058e86395b14756d7afc184f99f89dbc5ba0184e
Reviewed-on: https://go-review.googlesource.com/c/go/+/498715
Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: Than McIntosh <thanm@google.com>
Auto-Submit: Than McIntosh <thanm@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
diff --git a/src/cmd/go/alldocs.go b/src/cmd/go/alldocs.go
index 6a1cb8b..46466fd 100644
--- a/src/cmd/go/alldocs.go
+++ b/src/cmd/go/alldocs.go
@@ -3,7 +3,7 @@
 // license that can be found in the LICENSE file.
 
 // Code generated by 'go test cmd/go -v -run=TestDocsUpToDate -fixdocs'; DO NOT EDIT.
-// Edit the documentation in other files and rerun mkalldocs.sh to generate this one.
+// Edit the documentation in other files and then execute 'go generate cmd/go' to generate this one.
 
 // Go is a tool for managing Go source code.
 //
diff --git a/src/cmd/go/internal/help/help.go b/src/cmd/go/internal/help/help.go
index dd1f2f7..aeaba78 100644
--- a/src/cmd/go/internal/help/help.go
+++ b/src/cmd/go/internal/help/help.go
@@ -28,7 +28,7 @@
 		fmt.Fprintln(w, "// license that can be found in the LICENSE file.")
 		fmt.Fprintln(w)
 		fmt.Fprintln(w, "// Code generated by 'go test cmd/go -v -run=TestDocsUpToDate -fixdocs'; DO NOT EDIT.")
-		fmt.Fprintln(w, "// Edit the documentation in other files and rerun mkalldocs.sh to generate this one.")
+		fmt.Fprintln(w, "// Edit the documentation in other files and then execute 'go generate cmd/go' to generate this one.")
 		fmt.Fprintln(w)
 		buf := new(strings.Builder)
 		PrintUsage(buf, base.Go)