patches: matplotlib: add threading timeout patch for 3.11.1

Copy the same patch used for 3.11.0 to 3.11.1. We don't need the pytest
backport used for 3.11.0, since that is contained in the 3.11.1 release:

|tgamblin@alchemist ~/workspace/baylibre/rise/matplotlib ((HEAD detached at v3.11.1))$ git tag --contains cf5cebedbb
|v3.11.1

Signed-off-by: Trevor Gamblin <tgamblin@baylibre.com>

Author: threexc

patches/matplotlib/3.11.1/0001-tests-test_font_manager-increase-test_fontcache_thre.patch

@@ -0,0 +1,34 @@
+From a830afe01625f10e11640e2b2c3f3d88b2c16b36 Mon Sep 17 00:00:00 2001
+From: Trevor Gamblin <tgamblin@baylibre.com>
+Date: Tue, 21 Jul 2026 11:25:31 -0400
+Subject: [PATCH] tests: test_font_manager: increase test_fontcache_thread_safe
+ timeout
+
+This test seems to pass in a local riscv64 container, but fails when run
+on the native runners. It's a single threading test with a 10s timeout,
+so double that timeout for our builds. For now this should be considered
+inappropriate for upstream until we see the failure on their end too.
+
+Upstream-Status: Inappropriate [native runner specific]
+
+Signed-off-by: Trevor Gamblin <tgamblin@baylibre.com>
+---
+ lib/matplotlib/tests/test_font_manager.py | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/lib/matplotlib/tests/test_font_manager.py b/lib/matplotlib/tests/test_font_manager.py
+index add063df90..f3a9d57039 100644
+--- a/lib/matplotlib/tests/test_font_manager.py
++++ b/lib/matplotlib/tests/test_font_manager.py
+@@ -344,7 +344,7 @@ def _test_threading():
+ def test_fontcache_thread_safe():
+     pytest.importorskip('threading')
+ 
+-    subprocess_run_helper(_test_threading, timeout=10)
++    subprocess_run_helper(_test_threading, timeout=20)
+ 
+ 
+ def test_lockfilefailure(tmp_path):
+-- 
+2.55.0
+