Remove redundant variable from asset taskfile

The installation instructions for all templates that require the `DEFAULT_GO_PACKAGES` taskfile variable point to the
"go-task" asset taskfile as its source. However, there was a redundant copy of this variable in the "check-go-task" asset
taskfile.

Maintaining two copies of this fairly complex asset is difficult, for no benefit in return, so it must be removed.

Author: per1234

workflow-templates/assets/check-go-task/Taskfile.yml

@@ -1,10 +1,6 @@
 # See: https://taskfile.dev/#/usage
 version: "3"
 
-vars:
-  DEFAULT_GO_PACKAGES:
-    sh: echo $(go list ./... | tr '\n' ' ')
-
 tasks:
   # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/assets/check-go-task/Taskfile.yml
   go:check: