patch 8.2.1681: Vim9: unnessary :call commands in tests

Problem:    Vim9: unnessary :call commands in tests.
Solution:   Remove the commands. (issue #6936)
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index 7a1385c..de10724 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -279,7 +279,7 @@
     enddef
     Func([])
   END
-  call CheckScriptFailure(lines, 'E1013: argument 1: type mismatch, expected string but got list<unknown>', 5)
+  CheckScriptFailure(lines, 'E1013: argument 1: type mismatch, expected string but got list<unknown>', 5)
 enddef
 
 " Default arg and varargs
@@ -1099,7 +1099,7 @@
     enddef
     defcompile
   END
-  call writefile(lines, 'Xdef')
+  writefile(lines, 'Xdef')
   try
     source Xdef
     assert_report('should have failed')
@@ -1119,7 +1119,7 @@
     enddef
     defcompile
   END
-  call writefile(lines, 'Xdef')
+  writefile(lines, 'Xdef')
   try
     source Xdef
     assert_report('should have failed')
@@ -1138,7 +1138,7 @@
     defcompile
     Func()
   END
-  call writefile(lines, 'Xdef')
+  writefile(lines, 'Xdef')
   try
     source Xdef
     assert_report('should have failed')
@@ -1146,7 +1146,7 @@
     v:throwpoint->assert_match('_Func, line 3$')
   endtry
 
-  call delete('Xdef')
+  delete('Xdef')
 enddef
 
 def Test_deleted_function()