Do not stub Ruby version

Author: kddnewton

test/prism/api/parse_test.rb

@@ -148,15 +148,8 @@ def test_version_current
       end
 
       version = RUBY_VERSION.split(".").tap { |segments| segments[0] = segments[0].succ }.join(".")
-      stub_ruby_version(version) do
-        error = assert_raise(CurrentVersionError) { Prism.parse("1 + 1", version: "current") }
-        assert_includes error.message, "unknown"
-      end
-
-      stub_ruby_version("2.7.0") do
-        error = assert_raise(CurrentVersionError) { Prism.parse("1 + 1", version: "current") }
-        assert_includes error.message, "minimum"
-      end
+      assert_includes CurrentVersionError.new(version).message, "unknown"
+      assert_includes CurrentVersionError.new("2.7").message, "minimum"
     end
 
     def test_scopes
@@ -186,16 +179,5 @@ def find_source_file_node(program)
         queue.concat(node.compact_child_nodes)
       end
     end
-
-    def stub_ruby_version(version)
-      old_version = RUBY_VERSION
-
-      Object.send(:remove_const, :RUBY_VERSION)
-      Object.const_set(:RUBY_VERSION, version)
-      yield
-    ensure
-      Object.send(:remove_const, :RUBY_VERSION)
-      Object.const_set(:RUBY_VERSION, old_version)
-    end
   end
 end