patch 8.2.1766: Vim9: Some tests are still using :let
Problem: Vim9: Some tests are still using :let.
Solution: Change the last few declarations to use :var.
diff --git a/src/testdir/test_popupwin.vim b/src/testdir/test_popupwin.vim
index fdd9ac4..ea2ee3b 100644
--- a/src/testdir/test_popupwin.vim
+++ b/src/testdir/test_popupwin.vim
@@ -2690,7 +2690,7 @@
split
wincmd b
assert_equal(2, winnr())
- let buf = term_start(&shell, #{hidden: 1})
+ var buf = term_start(&shell, #{hidden: 1})
popup_create(buf, {})
TermWait(buf, 100)
popup_clear(true)