tex-luaotfload{,-doc}: update to 3.21

3.21
*  Fix performance regression introduced in version 3.19.
*  More reliably support TrueType based variable fonts in harf mode.

3.20
* Two critical bugs related to luaotfload-tool and the cache location have
  been corrected.

3.19
*  When used with LuaTeX 1.15.0 or newer, variable fonts are supported
  when using the harf shaper too.
*  A new algorithm for selecting fonts based on font family names allows
  to more reliably load fonts based on their family name.
*  The compiled font database gets compressed to reduce disk space and
  improve performance on newer systems.
*  Text automatically gets normalized to Unicode's NFC before shaping.
  This improves rendering for text written in decomposed forms for many
  fonts. This can be turned off by passing the -normalize font feature.
*  The fontloader has been synced with the context code from 2022-02-24.
  This fixes some broken rendering of TrueType based variable fonts.
*  A number of small bugfixes.

(markd)