remove stale variable from docs

Dependencies

• [2] PIEDOKYQ bugfix
• [3] ZPQI5UL3 bugfix: never use utf8 pos in string.sub
• [4] 3ZYCPNQY clearer copy
• [5] DBNRULIJ record one more case I can't automatically detect
• [*] BJ5X5O4A let's prevent the text cursor from ever getting on a drawing

Change contents

• replacement in Manual_tests.md at line 40
  [2.328]→[2.328:394](∅→∅)
  − sync. Any change to line data should clear line `fragments` and
  [2.328]

  [2.394]
  + sync. Any change to line data should clear the derived line property