patch 9.1.0587: tests: Test_gui_lowlevel_keyevent is still flaky

Problem:  tests: Test_gui_lowlevel_keyevent is still flaky
          (after v9.1.0571)
Solution: skip generating key event for Ctrl-C,
          remove the test_is_flaky variable again (Ken Takata)

v9.1.0571 was not enough.
Ctrl-C interruption may occur before the preceding events are processed.
Exclude Ctrl-C to avoid the flakiness.

closes: #15224

Signed-off-by: Ken Takata <kentkt@csc.jp>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index 428cd04..9ce9c8f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    587,
+/**/
     586,
 /**/
     585,