Fix dependency on pkg:js

PiperOrigin-RevId: 338130770
diff --git a/pubspec.yaml b/pubspec.yaml
index 9bbb27d..98c064f 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -17,7 +17,7 @@
 dev_dependencies:
   ffi: any
   fixnum: '>=0.9.0 <0.11.0'
-  js: 0.6.3-nullsafety
+  js: ^0.6.3-nullsafety
   test: ^1.16.0-nullsafety.4
 
 dependency_overrides: