fix(xlsx): XLSX emits std minified .text_as_html (#3558)
**Summary**
Eliminate historical "idiosyncracies" of `table.metadata.text_as_html`
HTML introduced by `partition_xlsx()`. Produce minified `.text_as_html`
consistent with that formed by chunking.
**Additional Context**
- XLSX `.text_as_html` is minified (no extra whitespace or thead, tbody,
tfoot elements).
- `table.text` is clean-concatenated-text (CCT) of table.
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Co-authored-by: scanny <scanny@users.noreply.github.com>
