Remove 1.15 deprecations
To be done after 1.14-stable is branched.
Scan the codebase for deprecations marked with a 1.15 deadline and remove them (ack deprecation.*1.15). All deprecations with a 1.15 deadline have been shipped (at least) in 1.13 and 1.14.
Marked for a 1.14.0 release so it's done at the time of 1.14-stable branching, but please move to 1.15.0 when done.