(rmail-ignored-headers): Remove extra paren.

lisp/mail/rmail.el

@@ -74,7 +74,7 @@ value is the user's name.)
 It is useful to set this variable in the site customization file.")
 
 ;;;###autoload
-(defvar rmail-ignored-headers "^via:\\|^mail-from:\\|^origin:\\|^status:\\|^received:\\|^x400-originator:\\|^x400-recipients:\\|^x400-received:\\|^x400-mts-identifier:\\|^x400-content-type:\\|^\\(resent-\\|\\)message-id:\\|^summary-line:\\|^resent-date:\\|^nntp-posting-host:\\|^path:\\|^x-char.*:\\|^x-face:\\|^x-mailer:")
+(defvar rmail-ignored-headers "^via:\\|^mail-from:\\|^origin:\\|^status:\\|^received:\\|^x400-originator:\\|^x400-recipients:\\|^x400-received:\\|^x400-mts-identifier:\\|^x400-content-type:\\|^\\(resent-\\|\\)message-id:\\|^summary-line:\\|^resent-date:\\|^nntp-posting-host:\\|^path:\\|^x-char.*:\\|^x-face:\\|^x-mailer:"
   "*Regexp to match header fields that Rmail should normally hide.")
 
 ;;;###autoload