Update the Git etiquette post to fix a typo

orgs/essays/git-etiquette.org

@@ -143,7 +143,7 @@ project too.
 
 There are seven easy rules that you can follow to rock your commit messages:
 
-1. Separate subject from body with a blank
+1. Separate subject from body with a blank line
 2. Limit the subject line to 50 characters
 3. Capitalize the subject line
 4. Do not end the subject line with a period