Fixing weird formatting in filter documentation

Request Type: docs

How to reproduce: Go to Filter documentation (http://docs.angularjs.org/api/ng/filter/filter), in the arguments table, compare the details column of `expression` with `comparator`, specifically after the line "Can be one of:"

Component(s): 

Impact: small

Complexity: small

This issue is related to: 

**Detailed Description:**

Minor changes in the docs: the `comparator` argument description in the filter documentation (http://docs.angularjs.org/api/ng/filter/filter) was looking really weird, as it should look like the `expression` argument doc - a simple list of possible data types.

**Other Comments:**