Fix/rephrase "unsaved changes" warning when cancelling a draft (#5610)

CHANGELOG

@@ -18,6 +18,7 @@ CHANGELOG Roundcube Webmail
 - Add rewrite rule to disable access to /vendor/bin folder in .htaccess (#5630)
 - Fix bug where it was too easy accidentally move a folder when using the subscription checkbox (#5655)
 - Managesieve: Fix parser issue with empty lines between comments (#5657)
+- Fix/rephrase "unsaved changes" warning when cancelling a draft (#5610)
 
 RELEASE 1.3-beta
 ----------------

program/localization/en_US/messages.inc

@@ -99,7 +99,7 @@ $messages['disclosedreciptitle'] = 'Too many public recipients';
 $messages['nosubjectwarning']  = 'The "Subject" field is empty. Would you like to enter one now?';
 $messages['nosubjecttitle']  = 'No subject';
 $messages['nobodywarning'] = 'Send this message without text?';
-$messages['notsentwarning'] = 'Message has not been sent. Do you want to discard your message?';
+$messages['notsentwarning'] = 'The message has not been sent and has unsaved changes. Do you want to discard your changes?';
 $messages['restoresavedcomposedata'] = 'A previously composed but unsent message was found.\n\nSubject: $subject\nSaved: $date\n\nDo you want to restore this message?';
 $messages['noldapserver'] = 'Please select an ldap server to search.';
 $messages['nosearchname'] = 'Please enter a contact name or email address.';