Fix so mime_content_type check in Installer uses files that should always be available (i.e. from program/resources) (#6599)

CHANGELOG

@@ -6,6 +6,7 @@ CHANGELOG Roundcube Webmail
 - Fix bug in parsing some IMAP command responses that include unsolicited replies (#6577)
 - Fix PHP 7.2 compatibility in debug_logger plugin (#6586)
 - Fix so ANY record is not used for email domain validation, use A, MX, CNAME, AAAA instead (#6581)
+- Fix so mime_content_type check in Installer uses files that should always be available (i.e. from program/resources) (#6599)
 
 RELEASE 1.3.8
 -------------

program/include/rcmail_install.php

@@ -519,10 +519,9 @@ class rcmail_install
     {
         $errors = array();
         $files  = array(
-            'skins/larry/images/roundcube_logo.png' => 'image/png',
+            'program/resources/tinymce/video.png' => 'image/png',
             'program/resources/blank.tiff'        => 'image/tiff',
             'program/resources/blocked.gif'       => 'image/gif',
-            'skins/larry/README'                    => 'text/plain',
         );
 
         foreach ($files as $path => $expected) {