Tiny typo

css-grid-2/Overview.bs

@@ -2869,7 +2869,7 @@ Placing Grid Items</h2>
  * If it has an explicit ''grid-row-start/span'' value,
  its [=grid span=] is <dfn export lt="explicit grid span|explicit row span|explicit column span|explicit span">explicit</dfn>.
  * Otherwise, its [=grid span=] is <dfn export lt="automatic grid span|automatic row span|automatic column span|automatic span">automatic</dfn>:
- if is [=subgridded=] in that axis,
+ if it is [=subgridded=] in that axis,
  its [=grid span=] is <a href="#subgrid-span">determined</a> from its <<line-name-list>>;
  otherwise its [=grid span=] is 1.
  </dl>