piem-b4-am-ready-from-mid: Use consistent spelling for message ID

It looks like all other spots that aren't specifically referring to
the header use "message ID".

1 files changed, 1 insertions, 1 deletions

diff --git a/piem-b4.el b/piem-b4.el
index 172236f..965840b 100644
--- a/piem-b4.el
+++ b/piem-b4.el
@@ -122,7 +122,7 @@ ARGS is a list of arguments to pass to `b4 am'."
 ;;;###autoload
 (defun piem-b4-am-ready-from-mid (mid &optional args)
   "Download the thread for MID and and extract an am-ready mbox.
-MID is a Message-Id to pass directly to `b4 am', along with the
+MID is a message ID to pass directly to `b4 am', along with the
 list of arguments specified via ARGS."
   (interactive (list (read-string "Message ID: " nil nil (piem-mid))
                      (transient-args 'piem-b4-am)))