docs: add deprecation warning

6 jobs for master in 60 minutes and 33 seconds (queued for 3 seconds)
latest
Status Job ID Name Coverage
  Test
passed #627307
macos_highsierra
test-macos

00:17:05

 
  Build
passed #627308
build-latest

00:42:22

passed #627309
build-nightly

00:32:11

 
  Docs
passed #627310
docs

00:00:49

 
  Deploy
passed #627311
pages

00:00:15

passed pages:deploy

00:00:00