Mention reference-types is enabled by default in ChangeLog (#22120)

Author: aheejin

ChangeLog.md

@@ -22,6 +22,8 @@ See docs/process.md for more on how version tagging works.
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 - The internal `read_` function was removed.  We now just use `readBinary` or
   `readAsync`. (#22080)
+- reference-types feature is now enabled by default in Emscripten, due to the
+  upstream LLVM change (https://github.com/llvm/llvm-project/pull/93261).
 
 3.1.61 - 05/31/24
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