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_vartabs.vim b/src/testdir/test_vartabs.vim
index 81e81b7..0d14aad 100644
--- a/src/testdir/test_vartabs.vim
+++ b/src/testdir/test_vartabs.vim
@@ -134,7 +134,7 @@
   bwipeout!
 endfunc
 
-func! Test_vartabs_breakindent()
+func Test_vartabs_breakindent()
   if !exists("+breakindent")
     return
   endif