patch 8.0.0334: can't access b:changedtick from a dict reference

Problem:    Can't access b:changedtick from a dict reference.
Solution:   Make changedtick a member of the b: dict. (inspired by neovim
            #6112)
diff --git a/src/testdir/test91.in b/src/testdir/test91.in
index e1365cb..c184ac3 100644
--- a/src/testdir/test91.in
+++ b/src/testdir/test91.in
@@ -1,4 +1,4 @@
-Tests for getbufvar(), getwinvar(), gettabvar() and gettabwinvar().
+Tests for getwinvar(), gettabvar() and gettabwinvar().
 vim: set ft=vim :
 
 STARTTEST
@@ -10,34 +10,7 @@
 :let t:testvar='abcd'
 :$put =string(gettabvar(1,'testvar'))
 :$put =string(gettabvar(1,'testvar'))
-:" Test for getbufvar()
-:let b:var_num = '1234'
-:let def_num = '5678'
-:$put =string(getbufvar(1, 'var_num'))
-:$put =string(getbufvar(1, 'var_num', def_num))
-:$put =string(getbufvar(1, ''))
-:$put =string(getbufvar(1, '', def_num))
-:unlet b:var_num
-:$put =string(getbufvar(1, 'var_num', def_num))
-:$put =string(getbufvar(1, ''))
-:$put =string(getbufvar(1, '', def_num))
-:$put =string(getbufvar(9, ''))
-:$put =string(getbufvar(9, '', def_num))
-:unlet def_num
-:$put =string(getbufvar(1, '&autoindent'))
-:$put =string(getbufvar(1, '&autoindent', 1))
 :"
-:" Open new window with forced option values
-:set fileformats=unix,dos
-:new ++ff=dos ++bin ++enc=iso-8859-2
-:let otherff = getbufvar(bufnr('%'), '&fileformat')
-:let otherbin = getbufvar(bufnr('%'), '&bin')
-:let otherfenc = getbufvar(bufnr('%'), '&fenc')
-:close
-:$put =otherff
-:$put =string(otherbin)
-:$put =otherfenc
-:unlet otherff otherbin otherfenc
 :" test for getwinvar()
 :let w:var_str = "Dance"
 :let def_str = "Chance"