Problem: tests: no test for displaying 'foldcolumn' with Unicode
"foldinner" in 'fillchars'.
Solution: Add a few more test cases. Also fix misplaced "foldinner"
entry in version9.txt (zeertzjq).
closes: #18483
Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>