run-command: fix a typo

Fix a typo in comments.

Signed-off-by: Andrew Kreimer <algonell@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: algonell

run-command.h

@@ -535,7 +535,7 @@ enum start_bg_result {
 	/* timeout expired waiting for child to become "ready" */
 	SBGR_TIMEOUT,
 
-	/* child process exited or was signalled before becomming "ready" */
+	/* child process exited or was signalled before becoming "ready" */
 	SBGR_DIED,
 };