Improve the semantic of seq-some

Improve the semantic of seq-some

Update seq-some to return non-nil if the predicate returns non-nil for
any element of the seq, in which case the returned value is the one
returned by the predicate.

* lisp/emacs-lisp/seq.el (seq-some): Update the function and its
  docstring.
* test/automated/seq-tests.el (test-seq-some): Add a regression test.
* doc/lispref/sequences.texi (Sequence Functions): Update the
  documentation for seq-some.