Bug#1006451: drop mimimi-maven-plugin as its only user was removed

[Thorsten Glaser]

reassign 1006451 ftp.debian.org
retitle 1006451 RM: minify-maven-plugin -- RoM; only remaining user gone
severity 1006451 normal
thanks

guacamole-client was RoQA'd in #926276
so this can be garbage-collected