[DRE-maint] Bug#989786: ruby-spamcheck: cannot use ruby-grpc package

[Pirate Praveen]

Package: ruby-spamcheck
Version: 0.1.0+git20210519.2084b44-2
Severity: grave
Control: block -1 by 966653

Since the only reverse dependency of ruby-spamcheck is gitlab and 
gitlab does not work with debian's ruby-grpc package (see #966653), 
dependency on ruby-grpc is removed. It will be added back when 
ruby-grpc can work with gitlab.