Add whatsnew entry for jit unique reference tracking

Author: eendebakpt

Doc/whatsnew/3.15.rst

@@ -1465,6 +1465,13 @@ Reiden Ong, Noam Cohen, Tomas Roun, PuQing, Cajetan Rodrigues, and Sacul in :gh:
 The JIT optimizer now supports significantly more operations than in 3.14.
 (Contributed by Kumar Aditya, Ken Jin, and Sacul in :gh:`131798`.)
 
+By tracking unique references to objects, the JIT optimizer can now eliminate
+reference count updates and perform inplace operations on ints and floats.
+(Contributed by Reiden Ong, and Pieter Eendebak in :gh:`143414` and :gh:`146306`.)
+
+The JIT optimizer now supports significantly more operations than in 3.14.
+(Contributed by Kumar Aditya, Ken Jin, and Sacul in :gh:`131798`.)
+
 .. rubric:: Better machine code generation
 
 The JIT compiler's machine code generator now produces better machine code