docs: remove the note saying that nanorc files must be in Unix format

Since commit 98f038ad from a month ago, nanorc files do not need to be
in Unix format (LF) but may also be in DOS (CR+LF) and Mac (CR) format.

doc/nano.texi

@@ -690,9 +690,8 @@ The following global toggles are available:
 @node Nanorc Files
 @chapter Nanorc Files
 
-The nanorc files contain the default settings for @command{nano}.  They
+The nanorc files contain the default settings for @command{nano}.  During
-should be in Unix format, not in DOS or Mac format.  During startup,
+startup, if @option{--rcfile} is not given, @command{nano} will read two files:
-if @option{--rcfile} is not given, @command{nano} will read two files:
 first the system-wide settings, from @file{/etc/nanorc} (the exact path
 might be different on your system), and then the user-specific settings,
 either from @file{~/.nanorc} or from @file{$XDG_CONFIG_HOME/nano/nanorc}

doc/nanorc.5

@@ -22,10 +22,9 @@
 nanorc \- GNU nano's configuration file
 
 .SH DESCRIPTION
-The \fInanorc\fP files contain the default settings for \fBnano\fP, a
+The \fInanorc\fP files contain the default settings for \fBnano\fP,
-small and friendly editor.  They should be in Unix format, not in
+a small and friendly editor.  During startup, if \fB\-\-rcfile\fR
-DOS or Mac format.  During startup, if \fB\-\-rcfile\fR is not given,
+is not given, \fBnano\fR will read two files: first the
-\fBnano\fR will read two files: first the
 system-wide settings, from \fI/etc/nanorc\fP (the exact path might be
 different on your system), and then the user-specific settings, either
 from \fI~/.nanorc\fR or from \fI$XDG_CONFIG_HOME/nano/nanorc\fR

doc/sample.nanorc.in

@@ -1,15 +1,12 @@
 ## Sample initialization file for GNU nano.
 ##
-## This file should not be in DOS or Mac format, and characters
+## Characters that are special in a shell should not be escaped here.
-## specially interpreted by the shell should not be escaped here.
+## Inside string parameters, quotes should not be escaped -- the last
-##
-## To make sure an option is disabled, use "unset <option>".
-##
-## For the options that take parameters, the default value is given.
-## Other options are unset by default.
-##
-## Inside string parameters, quotes should not be escaped.  The last
 ## double quote on the line will be seen as the closing quote.
+##
+## For the options that take parameters, the default value is shown.
+## Other options are unset by default.  To make sure that an option
+## is disabled, you can use "unset <option>".
 
 ## Make the 'nextword' function (Ctrl+Right) stop at word ends
 ## instead of at beginnings.