patch 9.0.0363: common names in test files causes tests to be flaky

Problem:    Common names in test files causes tests to be flaky.
Solution:   Use more specific names.
diff --git a/src/testdir/test_visual.vim b/src/testdir/test_visual.vim
index cde70bd..31ce829 100644
--- a/src/testdir/test_visual.vim
+++ b/src/testdir/test_visual.vim
@@ -1472,7 +1472,7 @@
 func Test_visual_area_adjusted_when_hiding()
   " The Visual area ended after the end of the line after :hide
   call setline(1, 'xxx')
-  vsplit Xfile
+  vsplit Xvaafile
   call setline(1, 'xxxxxxxx')
   norm! $o
   hid