More CI palliatives: lock to addressable 2.2.4.
More CI palliatives: lock to addressable 2.2.4.

Specifically, there seems to be a bad interaction between addressable
2.2.4, webmock 1.6.2, and the way Castanet's test suite uses webmock.
As the library code of Castanet doesn't use addressable for anything,
we'll just let those two libraries sort it out and remove the version
lock if/when that happens.

NUBIC/castanet