[PRISM] Run test setting global constant separately

This impacted other tests. Please mind the commons.

      /home/runner/work/ruby/ruby/src/test/ruby/test_compile_prism.rb:394: warning: already initialized constant Bar
      /tmp/test_reline_config_60145/bazbarbob.rb:6: warning: previous definition of Bar was here

        1) Failure:
      TestModule#test_const_get_evaled [/home/runner/work/ruby/ruby/src/test/ruby/test_module.rb:1239]:
      NameError expected but nothing was raised.

test/ruby/test_compile_prism.rb

@@ -388,6 +388,7 @@ module Prism
     end
 
     def test_ConstantPathTargetNode
+      assert_separately([], <<~'RUBY')
         verbose = $VERBOSE
         # Create some temporary nested constants
         Object.send(:const_set, "MyFoo", Object)
@@ -400,12 +401,7 @@ module Prism
         prism_eval = iseq.eval
         $VERBOSE = verbose
         assert_equal prism_eval, Object
-    ensure
-      ## Teardown temp constants
-      Object.const_get("MyFoo").send(:remove_const, "Bar")
-      Object.send(:remove_const, "MyFoo")
-      Object.send(:remove_const, "MyBar")
-      $VERBOSE = verbose
+      RUBY
     end
 
     def test_GlobalVariableTargetNode