Restore "colorrows" latex table style once CI runs Sphinx >=9.1.1

[chrisjsewell]

#1154 set latex_table_style = ["booktabs"] in docs/conf.py to work around TeX Live 2026's colortbl update, which makes Sphinx's colorrows implementation self-referential and crashes the PDF docs build with TeX capacity exceeded at the first table (upstream: sphinx-doc/sphinx#14465).

The upstream fix is milestoned for Sphinx 9.1.1, which is not yet released (latest is 9.1.0 as of 2026-07-12).

Once the docs CI job installs a Sphinx release containing the fix:

• remove the latex_table_style line (and its comment) from docs/conf.py to restore the default ["booktabs", "colorrows"] row shading in the PDF
• confirm the build-doc-formats latex job still passes

Cosmetic only — until then PDF tables just lose alternating row colours.