patch 8.2.4010: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more error messages to errors.h.
diff --git a/src/popupwin.c b/src/popupwin.c
index a556f68..0702222 100644
--- a/src/popupwin.c
+++ b/src/popupwin.c
@@ -1883,7 +1883,7 @@
 #ifdef FEAT_TERMINAL
 	    if (buf->b_term != NULL && popup_terminal_exists())
 	    {
-		emsg(_("E861: Cannot open a second popup with a terminal"));
+		emsg(_(e_cannot_open_second_popup_with_terminal));
 		return NULL;
 	    }
 #endif
@@ -3162,7 +3162,7 @@
     if (WIN_IS_POPUP(curwin) && curbuf->b_term != NULL
 					   && term_job_running(curbuf->b_term))
     {
-	emsg(_("E863: Not allowed for a terminal in a popup window"));
+	emsg(_(e_not_allowed_for_terminal_in_popup_window));
 	return TRUE;
     }
     return FALSE;