Fix manual workflow dispatch for validate

Author: hasufell

.github/workflows/validate.yml

@@ -19,6 +19,16 @@ on:
   release:
     types:
       - created
+  workflow_dispatch:
+    inputs:
+      allow-newer:
+        description: allow-newer line
+        required: false
+        type: string
+      constraints:
+        description: constraints line
+        required: false
+        type: string
 
 env:
   # We choose a stable ghc version across all os's