[wpimath] Pass Translation2d by const reference instead of by value

[MichaelLesirge]

Quick fix to update nearest method of Translation2d to pass values by const ref instead of by value in min_element's llamada.

When adding the Translation3d method, calcmogul noticed both C++ translation methods needed a fix.

Translation2d should be updated similarly, now that I'm looking at it. The rule of thumb is to pass anything larger than the machine word size (e.g., 32 bits on a 32-bit system) by const ref.
Separate branch/PR.