patch 9.0.0131: virtual text with Tab is not displayed correctly

Problem:    Virtual text with Tab is not displayed correctly.
Solution:   Change any Tab to a space.
diff --git a/src/testdir/test_textprop.vim b/src/testdir/test_textprop.vim
index 2a74dc7..832343d 100644
--- a/src/testdir/test_textprop.vim
+++ b/src/testdir/test_textprop.vim
@@ -2197,7 +2197,7 @@
       call prop_type_add('otherprop', #{highlight: 'Search'})
       call prop_type_add('moreprop', #{highlight: 'DiffAdd'})
       call prop_add(1, 18, #{type: 'someprop', text: 'SOME '})
-      call prop_add(1, 38, #{type: 'otherprop', text: 'OTHER '})
+      call prop_add(1, 38, #{type: 'otherprop', text: "OTHER\t"})
       call prop_add(1, 69, #{type: 'moreprop', text: 'MORE '})
       redraw
       normal $
@@ -2222,7 +2222,7 @@
       call prop_type_add('afterprop', #{highlight: 'Search'})
       call prop_type_add('belowprop', #{highlight: 'DiffAdd'})
       call prop_add(1, 0, #{type: 'rightprop', text: ' RIGHT ', text_align: 'right'})
-      call prop_add(1, 0, #{type: 'afterprop', text: ' AFTER ', text_align: 'after'})
+      call prop_add(1, 0, #{type: 'afterprop', text: "\tAFTER\t", text_align: 'after'})
       call prop_add(1, 0, #{type: 'belowprop', text: ' BELOW ', text_align: 'below'})
 
       call setline(2, 'Last line.')