patch 9.1.1182: No cmdline completion for 'completefuzzycollect'

Problem:  No cmdline completion for the 'completefuzzycollect' option
          (after v9.1.1178)
Solution: Add cmdline completion for the 'completefuzzycollect' option,
          improve its description in optwin.vim (zeertzjq).

closes: #16813

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_options.vim b/src/testdir/test_options.vim
index 84a0035..6a561ac 100644
--- a/src/testdir/test_options.vim
+++ b/src/testdir/test_options.vim
@@ -501,6 +501,7 @@
   endif
   call assert_equal('.', getcompletion('set complete=', 'cmdline')[1])
   call assert_equal('menu', getcompletion('set completeopt=', 'cmdline')[1])
+  call assert_equal('keyword', getcompletion('set completefuzzycollect=', 'cmdline')[0])
   if exists('+completeslash')
     call assert_equal('backslash', getcompletion('set completeslash=', 'cmdline')[1])
   endif