Proposal to remove ruby-rack-mount from the archive

[Pirate Praveen <praveen@onenetbeyond.org>]

Hi,

ruby-rack-mount had last upstream release in 2011 and its only reverse 
build dependency was ruby-addressable which did not use it anymore (I 
update the package to remove this build dependency). There is 
autopkgtest regression with ruby-rack 2.2.3 so if anyone is still 
interested to keep this package, please fix the regression. If no one 
is interested, I propose we remove this package.

Thanks
Praveen