[newlib-cygwin/cygwin-3_6-branch] Cygwin: Add recent OPEN_MAX fix into release note

[Jon Turney]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=620ad4894bf820f6e772b1b9e10a253609191f72

commit 620ad4894bf820f6e772b1b9e10a253609191f72
Author: Jon Turney <jon.turney@dronecode.org.uk>
Date:   Wed Jun 10 13:55:34 2026 +0100

    Cygwin: Add recent OPEN_MAX fix into release note
    
    Fixes: 31bf91f867c5 ("Cygwin: Ensure unused fd available for open()")
    Signed-off-by: Jon Turney <jon.turney@dronecode.org.uk>
    (cherry picked from commit 35fcbb8cfbccc34d02611d54a06731dfcc075578)

Diff:
---
 winsup/cygwin/release/3.6.10 | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/winsup/cygwin/release/3.6.10 b/winsup/cygwin/release/3.6.10
index a6647a822..e29c3d6c0 100644
--- a/winsup/cygwin/release/3.6.10
+++ b/winsup/cygwin/release/3.6.10
@@ -5,3 +5,6 @@ Fixes:
   Addresses: https://github.com/msys2/msys2-runtime/issues/338
 
 - Fix handling of surrogate pair in legacy console.
+
+- Fix behaviour with OPEN_MAX files open
+  Addresses: https://cygwin.com/pipermail/cygwin/2026-May/259664.html