patch 8.2.0250: test_clear_search_pat() is unused

Problem:    test_clear_search_pat() is unused.
Solution:   Remove the function. (Yegappan Lakshmanan, closes #5624)
diff --git a/src/testdir/test_writefile.vim b/src/testdir/test_writefile.vim
index 98a06eb..f616980 100644
--- a/src/testdir/test_writefile.vim
+++ b/src/testdir/test_writefile.vim
@@ -214,6 +214,10 @@
   call assert_fails('1,2write', 'E140:')
   close!
 
+  call assert_fails('w > Xtest', 'E494:')
+
+  call assert_fails('w > Xtest', 'E494:')
+
   " Try to overwrite a directory
   if has('unix')
     call mkdir('Xdir1')