OWNERS: adjust matchers

Two changes:

- The proper keyword is 'matchers' and not 'matches'.
- 'exact' only works on a file and not a directory because
  git doesn't track directories.  Switch directory to 'partial_regex'.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I98c1669e06a8572da94d176ab57c6b3179f8f319