Fix tab spacing in include/vcl/outdev.hxx

Change-Id: I98eb64ee6ebad72b534bac8a467a9a334876c2e6
Reviewed-on: https://gerrit.libreoffice.org/8758
Tested-by: Chris Sherlock <chris.sherlock79@gmail.com>
Reviewed-by: Chris Sherlock <chris.sherlock79@gmail.com>