[newlib-cygwin] Cygwin: Add pthread_key fix in release note

[Takashi Yano]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=42df80dad0794d9b3a4c178e35f7e7365c902513

commit 42df80dad0794d9b3a4c178e35f7e7365c902513
Author: Takashi Yano <takashi.yano@nifty.ne.jp>
Date:   Tue Apr 8 23:26:04 2025 +0900

    Cygwin: Add pthread_key fix in release note
    
    Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>

Diff:
---
 winsup/cygwin/release/3.6.1 | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/winsup/cygwin/release/3.6.1 b/winsup/cygwin/release/3.6.1
index 15eaf4884..e24766d01 100644
--- a/winsup/cygwin/release/3.6.1
+++ b/winsup/cygwin/release/3.6.1
@@ -45,3 +45,7 @@ Fixes:
 - Fix up cached DOS attributes when trying to create the same file in
   two (or more) threads/processes concurrently.
   Addresses: https://cygwin.com/pipermail/cygwin/2025-April/257871.html
+
+- Fix deadlock when calling pthread_key_create in the destructor of
+  a pthread_key.
+  Addresses: https://cygwin.com/pipermail/cygwin/2025-March/257705.html