Remove SCRIPT_ROOT, CODEGEN_PKG and KNATIVE_CODEGEN_PKG env 😅
Remove SCRIPT_ROOT, CODEGEN_PKG and KNATIVE_CODEGEN_PKG env 😅

Those environment variables are not used in the rest of the script and
thus consume resources (`go list …`) for nothing.

Signed-off-by: Vincent Demeester <b98c0fd48a8945096c766de790fe70420dd2f223@redhat.com>

tektoncd/pipeline,tektoncd/pipeline