Undeprecate CommandManager#register(String, Command, String...)

This is a very convenient shorthand so let's save it from being axed. This is a change I made for an eventual Velocity 2.0.0 but it is backwards compatible for 1.1.0.

api/src/main/java/com/velocitypowered/api/command/CommandManager.java

@@ -46,9 +46,7 @@ public interface CommandManager {
    * @param command the command to register
    * @param otherAliases additional aliases
    * @throws IllegalArgumentException if one of the given aliases is already registered
-   * @deprecated Prefer {@link #register(CommandMeta, Command)} instead.
    */
-  @Deprecated
   void register(String alias, Command command, String... otherAliases);
 
   /**