docs: improve comment consistency in .muttrc example configuration

Added a space to align comment formatting; this helps improve
consistency and visual uniformity.
Signed-off-by: Jiamu Sun <barroit@linux.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/SY0P300MB0801D1A4B278157CA7C92DE2CEBC2@SY0P300MB0801.AUSP300.PROD.OUTLOOK.COM

Documentation/process/email-clients.rst

@@ -216,7 +216,7 @@ Mutt is highly customizable. Here is a minimum configuration to start
 using Mutt to send patches through Gmail::
 
   # .muttrc
-  # ================  IMAP ====================
+  # ================  IMAP  ====================
   set imap_user = 'yourusername@gmail.com'
   set imap_pass = 'yourpassword'
   set spoolfile = imaps://imap.gmail.com/INBOX