archivers/fastjar: remove undue deprecation of maintained port

Despite its age the program still works fine and is indeed much
faster than reference implementation: e.g., packing the game's
resources for `games/sokobano' port can take over half a second
with /usr/local/openjdk8/bin/jar on my laptop, depending on the
system's load, while it's ~0.03 with fastjar.