parse 'any' as VersionConstraint.any

pkgs/pub_semver/lib/src/version_constraint.dart

diff --git a/pkgs/pub_semver/lib/src/version_constraint.dart b/pkgs/pub_semver/lib/src/version_constraint.dart
index f67375f..ab035ff 100644
--- a/pkgs/pub_semver/lib/src/version_constraint.dart
+++ b/pkgs/pub_semver/lib/src/version_constraint.dart
@@ -46,7 +46,7 @@
   ///     >2.0.4 <= 2.4.6
   factory VersionConstraint.parse(String text) {
     // Handle the "any" constraint.
-    if (text.trim() == "any") return new VersionRange();
+    if (text.trim() == "any") return any;
 
     var originalText = text;
     var constraints = [];