add changelog entry for #2872

Author: anmonteiro

CHANGES.md

@@ -8,6 +8,8 @@
   [#2855](https://github.com/reasonml/reason/pull/2855))
 - printer: pad record braces with spaces (@anmonteiro,
   [#2859](https://github.com/reasonml/reason/pull/2859))
+- printer: don't escape infix keywords (@syaiful6,
+  [#2872](https://github.com/reasonml/reason/pull/2859))
 
 ## 3.16.0