[docs] Add wpiunits to JavaDocs (#5793)

Co-authored-by: Sam Carlberg <sam.carlberg@gmail.com>

wpiunits/src/main/java/edu/wpi/first/units/Per.java

@@ -44,7 +44,7 @@ public class Per<N extends Unit<N>, D extends Unit<D>> extends Unit<Per<N, D>> {
    * denominator with a unit of time is discouraged; use {@link Velocity} instead.
    *
    * <pre>
-   *   Per.combine(Volts, Meters) // => possible PID constant
+   *   Per.combine(Volts, Meters) // possible PID constant
    * </pre>
    *
    * <p>It's recommended to use the convenience function {@link Unit#per(Unit)} instead of calling