patch 8.2.1020: popupwin test fails in the GUI

Problem:    Popupwin test fails in the GUI.
Solution:   Send GUI byte sequence for <C-S-a>.

src/testdir/test_popupwin.vim

@@ -3349,7 +3349,11 @@ func Test_popupwin_filter_input_multibyte()
 
   if has('unix')
     " with modifyOtherKeys <M-S-a> does not include a modifier sequence
+    if has('gui_running')
+      call feedkeys("\x9b\xfc\x08A", 'Lx!')
+    else
       call feedkeys("\<Esc>[27;4;65~", 'Lx!')
+    endif
     call assert_equal([0xc3, 0x81], g:bytes)
   endif
 

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1020,
 /**/
     1019,
 /**/