[New Multicolumn] Remove unnecessary calls to setRegionBasedColumnsEnabled.

Tests which enable region based multicolumn behavior using Javascript
don't need to do that anymore, because they are run via
virtual/regionbasedmulticol, which enables the new behavior using a
command line flag.

Note that tests in fast/multicol/newmulticol/compare-with-old-impl still
need to call internals.settings.setRegionBasedColumnsEnabled(true). They
are now the only tests which need to do so. (And it should remain like
that until they are removed during Issue 350853).

BUG=334335
R=rune@opera.com

Review URL: https://codereview.chromium.org/341103002

git-svn-id: svn://svn.chromium.org/blink/trunk@177528 bbb929c8-8fbe-4397-9dbb-9b2b20218538