[DRE-maint] ruby-grape is marked for autoremoval from testing

[Debian testing autoremoval watch]

ruby-grape 0.16.2-2 is marked for autoremoval from testing on 2018-03-08

It (build-)depends on packages with these RC bugs:
888127: ruby-grape-entity: FTBFS on ruby2.5: syntax error, unexpected '{'
888190: ruby-mustermann19: FTBFS on ruby2.5: TypeError: Integer