gruntfile: clean collection after unzipping

Co-authored-by: Alberto Merino <amerinor01@gmail.com>
Co-authored-by: Enric Morales <me@enric.me>
Co-authored-by: Roland Coeurjoly <rolandcoeurjoly@gmail.com>

If we run the `clean:collection` task after unzipping, we allow
downloading the file manually into the cache directory so that the unzip
task doesn't try downloading it again.

Gruntfile.js

@@ -693,9 +693,9 @@ module.exports = function (grunt) {
   //-- This task is called in the npm postinstallation
   //-- (after npm install is executed)
   grunt.registerTask("getcollection", [
-    "clean:collection",  //-- Remove previous collection downloaded
     "wget:collection",   //-- Download the collection
     "unzip"              //-- Unzip the collection (install it)
+    "clean:collection",  //-- Remove previously downloaded collection
   ]);
 
   //-- grunt server