gopls/doc/emacs.md: use more precise before-save terminology

Change-Id: I7ce5818c2067ae687ce3258189701396a2eea8cb
Reviewed-on: https://go-review.googlesource.com/c/tools/+/592335
Reviewed-by: Alan Donovan <[email protected]>
Auto-Submit: Michael Stapelberg <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: stapelberg

gopls/doc/emacs.md

@@ -111,9 +111,9 @@ project root.
 ;; Optional: install eglot-format-buffer as a save hook.
 ;; The depth of -10 places this before eglot's willSave notification,
 ;; so that that notification reports the actual contents that will be saved.
-(defun eglot-format-buffer-on-save ()
+(defun eglot-format-buffer-before-save ()
   (add-hook 'before-save-hook #'eglot-format-buffer -10 t))
-(add-hook 'go-mode-hook #'eglot-format-buffer-on-save)
+(add-hook 'go-mode-hook #'eglot-format-buffer-before-save)
 ```
 
 ### Configuring `gopls` via Eglot