patch 8.2.2678: test for 'autoshelldir' does not reset the option

Problem:    Test for 'autoshelldir' does not reset the option.
Solution:   Reset the option after testing.
diff --git a/src/testdir/test_terminal3.vim b/src/testdir/test_terminal3.vim
index ab926b6..f4cc38a 100644
--- a/src/testdir/test_terminal3.vim
+++ b/src/testdir/test_terminal3.vim
@@ -502,6 +502,8 @@
     let expected = tmpfolder
   endif
   call assert_equal(expected, getcwd(winnr()))
+
+  set noasd
 endfunc
 
 " Test for modeless selection in a terminal