.github: fix parallel typo in dispatch

Fixes: 874c0a5 Use massive parallel in workflow for PRs

Signed-off-by: Richard Alpe <[email protected]>

Author: rical

.github/workflows/build.yml

@@ -8,7 +8,7 @@ on:
         required: false
         default: ''
         type: string
-      parallell:
+      parallel:
         description: 'Massive parallel build of each image'
         required: false
         default: true