[docs] Update Doxypress version to 1.4.2

Author: rleh

docs/src/guide/installation.md

@@ -70,7 +70,7 @@ We use [Doxypress][doxypress_binaries] to generate the API documentation:
 
 ```sh
 sudo mkdir /opt/doxypress
-wget -O- https://download.copperspice.com/doxypress/binary/doxypress-1.4.1-ubuntu20.04-x64.tar.bz2 | sudo tar xj -C /opt/doxypress
+wget -O- https://github.com/copperspice/doxypress/releases/download/dp-1.4.2/doxypress-1.4.2-ubuntu20.04-x64.tar.bz2 | sudo tar xj -C /opt/doxypress
 ```
 
 Add the directory to your `PATH` variable in `~/.bashrc`: