patch 8.2.1578: Vim9: popup_clear() does not take "true" as argument

Problem:    Vim9: popup_clear() does not take "true" as argument.
Solution:   Use tv_get_bool(). (closes #6826)
diff --git a/src/version.c b/src/version.c
index 5232e84..12d49bb 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1578,
+/**/
     1577,
 /**/
     1576,