Updated CHANGELOG

(cherry picked from commit 4f56734a)

CHANGELOG.md

@@ -5,6 +5,7 @@ v4.3.2
 ------
 **Library**:
 - Add small optimisation for DriverAdaptive (!618)
+- Updated FFTW build to use the compiler used for building Nektar++ (!629)
 
 **Packaging**:
 - Fixes for DEB package dependencies (!630)