minor #14136 fix link to ChainAdapter::prune method (pableu)

This PR was submitted for the master branch but it was merged into the 3.4 branch instead.

Discussion
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fix link to `ChainAdapter::prune` method

The link doesn't work otherwise.

Commits
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c22f5b9 fix link to `ChainAdapter::prune` method

Author: javiereguiluz

components/cache/adapters/chain_adapter.rst

@@ -44,7 +44,7 @@ slowest storage engines, :class:`Symfony\\Component\\Cache\\Adapter\\ApcuAdapter
         new FilesystemAdapter(),
     ]);
 
-When calling this adapter's :method:`Symfony\\Component\\Cache\\ChainAdapter::prune` method,
+When calling this adapter's :method:`Symfony\\Component\\Cache\\Adapter\\ChainAdapter::prune` method,
 the call is delegated to all its compatible cache adapters. It is safe to mix both adapters
 that *do* and do *not* implement :class:`Symfony\\Component\\Cache\\PruneableInterface`, as
 incompatible adapters are silently ignored::