patch 8.2.4892: test failures because of changed error messages

Problem:    Test failures because of changed error messages.
Solution:   Adjust the exptected error messages.
diff --git a/src/testdir/test_expand.vim b/src/testdir/test_expand.vim
index 4f5bb67..cd537f4 100644
--- a/src/testdir/test_expand.vim
+++ b/src/testdir/test_expand.vim
@@ -141,7 +141,7 @@
   if RunVim([], [], '--clean -s Xscript')
     call assert_equal([
           \ 'E1274: No script file name to substitute for "<script>"',
-          \ 'E498: no :source file name to substitute for "<sfile>"'],
+          \ 'E498: No :source file name to substitute for "<sfile>"'],
           \ readfile('Xresult'))
   endif
   call delete('Xscript')