[css-ui-3] Remove obsolete tests

The tests removed refered to box-sizing:padding-box, which has been removed from the specification.
w3c · frivoal · Nov 29, 2016 · Nov 29, 2016 · Nov 29, 2016 · 40a68a5862300dc079a8126800a0807f11871a6b
commit 40a68a5862300dc079a8126800a0807f11871a6b
diff --git a/css-ui-3/box-sizing-002.html b/css-ui-3/box-sizing-002.html
diff --git a/css-ui-3/box-sizing-004.html b/css-ui-3/box-sizing-004.html
diff --git a/css-ui-3/box-sizing-006.html b/css-ui-3/box-sizing-006.html
diff --git a/css-ui-3/zcorpan/box-sizing-padding-box-block-001-ref.html b/css-ui-3/zcorpan/box-sizing-padding-box-block-001-ref.html
diff --git a/css-ui-3/zcorpan/box-sizing-padding-box-block-001.html b/css-ui-3/zcorpan/box-sizing-padding-box-block-001.html
diff --git a/css-ui-3/zcorpan/guide.txt b/css-ui-3/zcorpan/guide.txt