Update default Pack version to v0.39.1 (#391)

Signed-off-by: GitHub <noreply@github.com>
Co-authored-by: buildpack-bot <buildpack-bot@users.noreply.github.com>
Co-authored-by: Ed Morley <501702+edmorley@users.noreply.github.com>

Author: buildpack-bot

setup-pack/action.yml

@@ -6,7 +6,7 @@ inputs:
   pack-version:
     description: 'The version of pack to install'
     required:    false
-    default:     '0.39.0'
+    default:     '0.39.1'
 
 runs:
   using: "composite"