github: fix release.on to push.tags

Change-Id: I8532b16488226d5d7903aa57030005dbf13ca646
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/5660
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index c258d2f..3d29055 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -1,8 +1,9 @@
 name: Release
 
 on:
-  release:
-    types: [published]
+  push:
+    tags:
+      - 'v*'
 
 jobs:
   goreleaser: