go.dev: merge go.dev/_content into root _content

Many renames. And then adjust references.

Change-Id: I4d03c76dbc0bf4d070208d568861ee820904c0dc
Reviewed-on: https://go-review.googlesource.com/c/website/+/365097
Trust: Russ Cox <rsc@golang.org>
Reviewed-by: Jamal Carvalho <jamal@golang.org>
diff --git a/content.go b/content.go
index bcd741c..3b59616 100644
--- a/content.go
+++ b/content.go
@@ -10,13 +10,10 @@
 	"io/fs"
 )
 
-// Golang is the golang.org website's static content.
-var Golang fs.FS = subdir(embedded, "_content")
+// Content is the go.dev website's static content.
+var Content fs.FS = subdir(embedded, "_content")
 
-// Godev is the go.dev website's static content.
-var Godev fs.FS = subdir(embedded, "go.dev/_content")
-
-//go:embed _content go.dev/_content
+//go:embed _content
 var embedded embed.FS
 
 func subdir(fsys fs.FS, path string) fs.FS {