test_require.rb: use assert_separately

* test/ruby/test_require.rb: use assert_separately preferably to
  assert_in_out_err for clear messages.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42185 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
test_require.rb: same process

* test/ruby/test_require.rb (assert_require_nonascii_path): run in
  same process.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42186 b2dd03c8-39d4-4d8f-98ff-823fe69b080e