patch 8.2.1604: Vim9: cannot use "true" with getcompletion()

Problem:    Vim9: cannot use "true" with getcompletion().
Solution:   use tv_get_bool_chk(). (closes #6875)
diff --git a/src/cmdexpand.c b/src/cmdexpand.c
index 79fb006..3ef3e1d 100644
--- a/src/cmdexpand.c
+++ b/src/cmdexpand.c
@@ -2885,7 +2885,7 @@
     type = tv_get_string(&argvars[1]);
 
     if (argvars[2].v_type != VAR_UNKNOWN)
-	filtered = tv_get_number_chk(&argvars[2], NULL);
+	filtered = tv_get_bool_chk(&argvars[2], NULL);
 
     if (p_wic)
 	options |= WILD_ICASE;