minor #49916 [Security] Add SymfonyCasts as a backer of version 6.3 (nicolas-grekas)

This PR was merged into the 6.3 branch.

Discussion
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[Security] Add SymfonyCasts as a backer of version 6.3

| Q             | A
| ------------- | ---
| Branch?       | 6.3
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

Thanks them! 🙏

/cc `@weaverryan` *et al.*

Commits
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31f65d480e [Security] Add SymfonyCasts as a backer of version 6.3

Author: fabpot

README.md

@@ -15,7 +15,7 @@ $ composer require symfony/security-http
 Sponsor
 -------
 
-The Security component for Symfony 6.2 is [backed][1] by [SymfonyCasts][2].
+The Security component for Symfony 6.3 is [backed][1] by [SymfonyCasts][2].
 
 Learn Symfony faster by watching real projects being built and actively coding
 along with them. SymfonyCasts bridges that learning gap, bringing you video