This was introduced in commit 9c7ffb6b
([cbosdo03]Applied the patches to upstream, 2009-12-02), as setting the
outline level also set the NumberingStyleName to "Outline" as well,
which is not what we want.

Since then, commit b95d203b (Don't load
the default values of the styles in writerfilter, 2012-08-20) already
disabled default styles, so the previous manual clearing is no longer
necessary (testcases already fail if this later commit is reverted).

As a result, just remove this manual clearing, it's no longer necessary
and it is problematic, as it triggers copying the SvxLRSpaceItem from
the parent style with no good reason.

Change-Id: Ie17547a979a6b0feadbd2eed0f06e84fcb17fca6