os: fix broken comment's link

Change-Id: Icf6cb06dfdde00de1db5e57b243d7e60a9e4e7ac
GitHub-Last-Rev: 45003b0656dec68cf0bc1f32b3de2ab688875524
GitHub-Pull-Request: golang/go#35834
Reviewed-on: https://go-review.googlesource.com/c/go/+/208837Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/os/file.go

@@ -411,7 +411,7 @@ func UserCacheDir() (string, error) {
 // subdirectory within this one and use that.
 //
 // On Unix systems, it returns $XDG_CONFIG_HOME as specified by
-// https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html if
+// https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html if
 // non-empty, else $HOME/.config.
 // On Darwin, it returns $HOME/Library/Application Support.
 // On Windows, it returns %AppData%.