[HttpFoundation] CSRF warning docs on Request::enableHttpMethodParameterOverride()

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #12043 
| License       | MIT
| Doc PR        | /

Since I wanted to understand this issue I did some research and altered the comment block. Is this a clear enough explanation or does it need more?