[Security] Add SymfonyCasts as a backer to the READMEs

Author: nicolas-grekas

README.md

@@ -15,7 +15,7 @@ $ composer require symfony/security-http
 Sponsor
 -------
 
-The Security component for Symfony 6.1 is [backed][1] by [SymfonyCasts][2].
+The Security component for Symfony 6.2 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