minor #18530 [Testing] Mention the KernelBrowser::disableReboot method (MaximePinot)

This PR was merged into the 5.4 branch.

Discussion
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[Testing] Mention the `KernelBrowser::disableReboot` method

It would have been helpful to me to know about the `disableReboot` method while reading this caution block, so I think it will also be useful for others. 😊

Commits
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c34c5cb [Testing] Mention the `KernelBrowser::disableReboot` method

Author: javiereguiluz

testing.rst

@@ -622,6 +622,7 @@ This allows you to create all types of requests you can think of:
     Also, it means that entities loaded by Doctrine repositories will
     be "detached", so they will need to be refreshed by the manager or
     queried again from a repository.
+    You can disable this behavior by calling the :method:`disableReboot() <Symfony\\Bundle\\FrameworkBundle\\KernelBrowser::disableReboot>` method.
 
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