patch 8.2.1627: Vim9: cannot pass "true" to submatch/term_gettty/term_start

Problem:    Vim9: cannot pass "true" to submatch(), term_gettty() and
            term_start()
Solution:   Use tv_get_bool_chk(). (closes #6888, closes #6890, closes #6889)
diff --git a/src/terminal.c b/src/terminal.c
index cab9cb9..fe84a9f 100644
--- a/src/terminal.c
+++ b/src/terminal.c
@@ -5768,7 +5768,7 @@
     if (buf == NULL)
 	return;
     if (argvars[1].v_type != VAR_UNKNOWN)
-	num = tv_get_number(&argvars[1]);
+	num = tv_get_bool(&argvars[1]);
 
     switch (num)
     {