runtime(doc): Fix notation of "Vim script" and "Vim9 script"

closes: #17213

Signed-off-by: Hirohito Higashi <h.east.727@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_cmdline.vim b/src/testdir/test_cmdline.vim
index c4b7b57..9b2fee3 100644
--- a/src/testdir/test_cmdline.vim
+++ b/src/testdir/test_cmdline.vim
@@ -4267,7 +4267,7 @@
   " required for :*
   set cpo+=*
   let list = filter(getcompletion('', 'command'), 'exists(":" . v:val) == 0')
-  " :++ and :-- are only valid in Vim9 Script context, so they can be ignored
+  " :++ and :-- are only valid in Vim9 script context, so they can be ignored
   call assert_equal(['++', '--'], sort(list))
   call assert_equal(2, exists(':k'))
   call assert_equal(0, exists(':ke'))