RcppEnsmallen 0.2.22.1.1

• Upgraded to ensmallen 2.22.1: "E-Bike Excitement" (2024-12-03)
  • Remove unused variables to fix compiler warnings
    (#413).
• DESCRIPTION now emphasizes a C++14 or greater compiler and a requirement for
  Armadillo 10.8.2 or higher library.
  (#68).