fix(docx): fix short-row DOCX table (#2943)
**Summary**
The DOCX format allows a table row to start late and/or end early,
meaning cells at the beginning or end of a row can be omitted. While
there are legitimate uses for this capability, using it in practice is
relatively rare. However, it can happen unintentionally when adjusting
cell borders with the mouse. Accommodate this case and generate accurate
`.text` and `.metadata.text_as_html` for these tables.
