TST: not correctly using OrderedDict in test_series_apply
in Python versions <3.6 this syntax will result in an unordered dict

- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

@sylviawhoa : Thanks for reporting this!  Do you have a code-example or test where this was important?  We would like to be able to catch this in the future if it's actually important. @gfyoung @sinhrks If your testing environment uses Python 3.6, this issue would be undetectable because in Python 3.6 all dictionaries are ordered, in which case you wouldn't need OrderedDict() at all. For earlier versions, this test may fail because you are calling OrderedDict() on a dictionary, hence preserving a random order. 

I found this issue because I searched my entire repo for instances of `OrderedDict({` to find OrderedDict called on a dictionary (since that was a bug I had that caused my tests to fail with 3.5). I have pandas installed in my virtual environment so this came up in the search.

Not sure how important this really is because it's only in a test, but it is an issue.  thanks, this was a typo.