docs: v3.4.0 changelog

Author: kozistr

docs/changelogs/v3.4.0.md

@@ -6,7 +6,7 @@
     * [First Order Concentrated Updating Scheme](https://arxiv.org/abs/2501.12243) 
 * Implement `PSGD Kron` optimizer. (#337)
     * [preconditioned stochastic gradient descent w/ Kron pre-conditioner](https://arxiv.org/abs/1512.04202) 
-* Implement `EXAdam` optimizer. (#338)
+* Implement `EXAdam` optimizer. (#338, #339)
     * [The Power of Adaptive Cross-Moments](https://arxiv.org/abs/2412.20302)
 
 ### Update