minor symfony#13905 add deprecation contracts package (zairigimad)

This PR was submitted for the 5.1 branch but it was merged into the 4.4 branch instead.

Discussion
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add deprecation contracts package

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Commits
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f0d69b7 add deprecation contracts package

Author: javiereguiluz

components/contracts.rst

@@ -19,6 +19,7 @@ your projects really need:
 
     $ composer require symfony/cache-contracts
     $ composer require symfony/event-dispatcher-contracts
+    $ composer require symfony/deprecation-contracts
     $ composer require symfony/http-client-contracts
     $ composer require symfony/service-contracts
     $ composer require symfony/translation-contracts