Fix editor warnings in http_server and mime.

pkg/mime/lib/src/extension_map.dart

Index: pkg/mime/lib/src/extension_map.dart
diff --git a/pkg/mime/lib/src/extension_map.dart b/pkg/mime/lib/src/extension_map.dart
index 19286bbd2fca9543b7b926ef3aaf04c93a513363..ac534aea5c8111fc814fffae23b732190c570ff4 100644
--- a/pkg/mime/lib/src/extension_map.dart
+++ b/pkg/mime/lib/src/extension_map.dart
@@ -759,7 +759,6 @@ Map<String, String> _defaultExtensionMap = const <String, String>{
 'stl':'application/vnd.ms-pki.stl',
 'str':'application/vnd.pg.format',
 'stw':'application/vnd.sun.xml.writer.template',
-'sub':'image/vnd.dvb.subtitle',
 'sub':'text/vnd.dvb.subtitle',
 'sus':'application/vnd.sus-calendar',
 'susp':'application/vnd.sus-calendar',
@@ -903,7 +902,6 @@ Map<String, String> _defaultExtensionMap = const <String, String>{
 'wmv':'video/x-ms-wmv',
 'wmx':'video/x-ms-wmx',
 'wmz':'application/x-ms-wmz',
-'wmz':'application/x-msmetafile',
 'woff':'application/x-font-woff',
 'wpd':'application/vnd.wordperfect',
 'wpl':'application/vnd.ms-wpl',