patch 8.2.4913: popup_hide() does not always have effect

Problem:    Popup_hide() does not always have effect.
Solution:   Add the POPF_HIDDEN_FORCE flag. (closes #10376)
diff --git a/src/testdir/test_popupwin.vim b/src/testdir/test_popupwin.vim
index 3e5373c..f58b159 100644
--- a/src/testdir/test_popupwin.vim
+++ b/src/testdir/test_popupwin.vim
@@ -4055,7 +4055,7 @@
       setline(1, ['', 'some text', '', 'other text'])
       prop_type_add('someprop', {})
       prop_add(2, 9, {type: 'someprop', length: 5})
-      popup_create('attached to "some"', {
+      g:some_id = popup_create('attached to "some"', {
           textprop: 'someprop',
           highlight: 'ErrorMsg',
           line: -1,
@@ -4076,6 +4076,12 @@
   let buf = RunVimInTerminal('-S XtestPropNotVisble', #{rows: 10})
   call VerifyScreenDump(buf, 'Test_popup_prop_not_visible_01', {})
 
+  " check that hiding and unhiding the popup works
+  call term_sendkeys(buf, ":call popup_hide(g:some_id)\<CR>")
+  call VerifyScreenDump(buf, 'Test_popup_prop_not_visible_01a', {})
+  call term_sendkeys(buf, ":call popup_show(g:some_id)\<CR>")
+  call VerifyScreenDump(buf, 'Test_popup_prop_not_visible_01b', {})
+
   call term_sendkeys(buf, ":vert resize -14\<CR>")
   call VerifyScreenDump(buf, 'Test_popup_prop_not_visible_02', {})