patch 8.1.0711: test files still use function!

Problem:    Test files still use function!.
Solution:   Remove the exclamation mark.  Fix overwriting a function.
diff --git a/src/testdir/test_matchadd_conceal_utf8.vim b/src/testdir/test_matchadd_conceal_utf8.vim
index 34d3ee2..68792fb 100644
--- a/src/testdir/test_matchadd_conceal_utf8.vim
+++ b/src/testdir/test_matchadd_conceal_utf8.vim
@@ -7,19 +7,19 @@
   set term=ansi
 endif
 
-function! s:screenline(lnum) abort
+func s:screenline(lnum) abort
   let line = []
   for c in range(1, winwidth(0))
     call add(line, nr2char(screenchar(a:lnum, c)))
   endfor
   return s:trim(join(line, ''))
-endfunction
+endfunc
 
-function! s:trim(str) abort
+func s:trim(str) abort
   return matchstr(a:str,'^\s*\zs.\{-}\ze\s*$')
-endfunction
+endfunc
 
-function! Test_match_using_multibyte_conceal_char()
+func Test_match_using_multibyte_conceal_char()
   new
   setlocal concealcursor=n conceallevel=1
 
@@ -40,4 +40,4 @@
   call assert_equal(screenattr(lnum, 1), screenattr(lnum, 16))
 
   quit!
-endfunction
+endfunc