patch 8.1.2051: double-click test is a bit flaky

Problem:    Double-click test is a bit flaky.
Solution:   Correct entry in list of flaky tests.
diff --git a/src/testdir/runtest.vim b/src/testdir/runtest.vim
index 5623dc8..d9177e0 100644
--- a/src/testdir/runtest.vim
+++ b/src/testdir/runtest.vim
@@ -333,7 +333,7 @@
       \ 'Test_raw_one_time_callback()',
       \ 'Test_reltime()',
       \ 'Test_server_crash()',
-      \ 'Test_term_mouse_double_click_to_create_tab',
+      \ 'Test_term_mouse_double_click_to_create_tab()',
       \ 'Test_terminal_ansicolors_default()',
       \ 'Test_terminal_ansicolors_func()',
       \ 'Test_terminal_ansicolors_global()',