Convert raw strings in pub (and apidoc) to new syntax.

utils/pub/hosted_source.dart

Index: utils/pub/hosted_source.dart
diff --git a/utils/pub/hosted_source.dart b/utils/pub/hosted_source.dart
index 37ad288e1f65c30be8767e41737e3e8d76799430..3c4963419b877876a2e4b988067cd437f486b99f 100644
--- a/utils/pub/hosted_source.dart
+++ b/utils/pub/hosted_source.dart
@@ -96,8 +96,8 @@ class HostedSource extends Source {
    */
   String systemCacheDirectory(PackageId id) {
     var parsed = _parseDescription(id.description);
-    var url = parsed.last.replaceAll(new RegExp(@"^https?://"), "");
-    var urlDir = replace(url, new RegExp(@'[<>:"\\/|?*%]'), (match) {
+    var url = parsed.last.replaceAll(new RegExp(r"^https?://"), "");
+    var urlDir = replace(url, new RegExp(r'[<>:"\\/|?*%]'), (match) {
       return '%${match[0].charCodeAt(0)}';
     });
     return join(systemCacheRoot, urlDir, "${parsed.first}-${id.version}");