CHANGELOG: 1.15.0: Mention diff snapshot memory corruption bugfix

Update v1.15.0 CHANGELOG mentioning the fix for #5707:
#5705

Signed-off-by: Ilias Stamatis <ilstam@amazon.com>

Author: ilstam

CHANGELOG.md

@@ -22,6 +22,11 @@ and this project adheres to
 
 ### Added
 
+- [#5705](https://github.com/firecracker-microvm/firecracker/pull/5705): Fixed
+  a bug that caused Firecracker to corrupt the memory files of differential
+  snapshots for VMs with multiple memory slots. This affected VMs using memory
+  hot-plugging or any x86 VMs with a memory size larger than 3GiB.
+
 - [#5510](https://github.com/firecracker-microvm/firecracker/pull/5510),
   [#5593](https://github.com/firecracker-microvm/firecracker/pull/5593),
   [#5564](https://github.com/firecracker-microvm/firecracker/pull/5564): Add