This minor change has the following benefits:
- it follows the documented way for modern Ubuntu distros (this CI task uses jammy)
- it makes package installation time shorter as no need to install the
g++-mingw-w64-x86-64-win32package - (not directly related to this repo) in https://github.com/bitcoin-core/gui-qml Qt 5.15.3 (but not 5.15.2) build system goes wild otherwise