Move Pkg tests to node 1

This ensures that `Pkg` tests, which now use `redirect_stdin()` run on
node 1, which actually has an `stdin` available.

test/runtests.jl

@@ -77,6 +77,8 @@ move_to_node1("threads")
 move_to_node1("Distributed")
 # Ensure things like consuming all kernel pipe memory doesn't interfere with other tests
 move_to_node1("stress")
+# Pkg now uses `redirect_stdin()`, which fails unless its run on node 1
+move_to_node1("Pkg")
 
 # In a constrained memory environment, run the "distributed" test after all other tests
 # since it starts a lot of workers and can easily exceed the maximum memory