docs: add deprecation warning

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  Test
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macos_highsierra
test-macos

00:17:37

 
  Build
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build-latest

00:50:48

passed #629158
build-nightly

00:33:03

 
  Docs
passed #629159
docs

00:00:57

 
  Deploy
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pages

00:00:17

passed pages:deploy

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