[pkg/js] Update pubspec to 3.8

Change-Id: Icfba93065a6c9626b13d2147806e5f78b261e0c2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/427563
Commit-Queue: Nate Biggs <[email protected]>
Auto-Submit: Mayank Patke <[email protected]>
Reviewed-by: Nate Biggs <[email protected]>

Author: fishythefish

pkg/js/pubspec.yaml

@@ -7,7 +7,7 @@ topics:
  - interop
 
 environment:
-  sdk: ^3.7.0-0
+  sdk: ^3.8.0-0
 
 resolution: workspace