Fix a typo in ELisp manual

* doc/lispref/sequences.texi (Sequence Functions): Fix a typo.
(Bug#35817)

Copyright-paperwork-exempt: yes
1 job for emacs-26 in 25 minutes and 30 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #1877
test

00:25:30