Help: Add 4.1 release note for Renesas compiler support

This was missed in commit 514135f563 (Renesas: Add support for Renesas
compilers, 2025-04-14, v4.1.0-rc1~89^2).

Issue: #26880

Help/release/4.1.rst

@@ -56,6 +56,12 @@ Compilers
 
 .. _`Diab compilers from Wind River Systems`: https://www.windriver.com/resource/wind-river-diab-compiler-product-overview
 
+* `Renesas Compilers`_ are now supported with
+  :variable:`compiler id <CMAKE_<LANG>_COMPILER_ID>` ``Renesas`` for
+  languages ``ASM`` and ``C``.
+
+.. _Renesas Compilers: https://www.renesas.com
+
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