patch 8.1.2373: cannot build with +popupwin but without +quickfix

Problem:    Cannot build with +popupwin but without +quickfix. (John Marriott)
Solution:   Adjust #ifdefs.
diff --git a/src/testdir/test_mksession.vim b/src/testdir/test_mksession.vim
index a3712a3..dac7c54 100644
--- a/src/testdir/test_mksession.vim
+++ b/src/testdir/test_mksession.vim
@@ -355,6 +355,8 @@
 if has('terminal')
 
 func Test_mksession_terminal_shell()
+  CheckFeature quickfix
+
   terminal
   mksession! Xtest_mks.out
   let lines = readfile('Xtest_mks.out')
@@ -436,6 +438,8 @@
 endfunc
 
 func Test_mksession_terminal_restore_other()
+  CheckFeature quickfix
+
   terminal
   eval bufnr('%')->term_setrestore('other')
   mksession! Xtest_mks.out