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_utf8.vim b/src/testdir/test_utf8.vim
index 24e3db8..699df62 100644
--- a/src/testdir/test_utf8.vim
+++ b/src/testdir/test_utf8.vim
@@ -25,17 +25,17 @@
 endfunc
 
 " Test for customlist completion
-function! CustomComplete1(lead, line, pos)
+func CustomComplete1(lead, line, pos)
 	return ['あ', 'い']
-endfunction
+endfunc
 
-function! CustomComplete2(lead, line, pos)
+func CustomComplete2(lead, line, pos)
 	return ['あたし', 'あたま', 'あたりめ']
-endfunction
+endfunc
 
-function! CustomComplete3(lead, line, pos)
+func CustomComplete3(lead, line, pos)
 	return ['Nこ', 'Nん', 'Nぶ']
-endfunction
+endfunc
 
 func Test_customlist_completion()
   command -nargs=1 -complete=customlist,CustomComplete1 Test1 echo