Apply suggestions from code review

Co-authored-by: Sutou Kouhei <[email protected]>

Author: st0012

test/rdoc/test_rdoc_ri_driver.rb

@@ -1008,7 +1008,7 @@ def test_expand_name
 
     assert_equal 'Z', e.name
 
-    @driver.stores << RDoc::Store.new(@rdoc_options, path: nil, type: :system)
+    @driver.stores << RDoc::Store.new(@rdoc_options, type: :system)
 
     assert_equal 'ruby:README', @driver.expand_name('ruby:README')
     assert_equal 'ruby:',       @driver.expand_name('ruby:')
@@ -1085,7 +1085,7 @@ def test_filter_methods_not_found
   end
 
   def test_find_store
-    @driver.stores << RDoc::Store.new(@rdoc_options, path: nil, type: :system)
+    @driver.stores << RDoc::Store.new(@rdoc_options, type: :system)
     @driver.stores << RDoc::Store.new(@rdoc_options, path: 'doc/gem-1.0/ri', type: :gem)
 
     assert_equal 'ruby',    @driver.find_store('ruby')