patch 8.0.0884: can't specify the wait time for term_wait()

Problem:    Can't specify the wait time for term_wait().
Solution:   Add an otional second argument.
diff --git a/src/evalfunc.c b/src/evalfunc.c
index fde2058..2377d19 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -843,7 +843,7 @@
     {"term_scrape",	2, 2, f_term_scrape},
     {"term_sendkeys",	2, 2, f_term_sendkeys},
     {"term_start",	1, 2, f_term_start},
-    {"term_wait",	1, 1, f_term_wait},
+    {"term_wait",	1, 2, f_term_wait},
 #endif
     {"test_alloc_fail",	3, 3, f_test_alloc_fail},
     {"test_autochdir",	0, 0, f_test_autochdir},