[HttpFoundation] Changed httpMethodParameterOverride to reset method

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #9464
| License       | MIT
| Doc PR        | n/a

This PR fixes an issue where method parameter overriding fails if the ```getMethod``` is called BEFORE the overriding is enabled, because the value is cached. Now the method is reset when enabling the overriding, so that ```getMethod()``` will check again.

See https://github.com/symfony/symfony/issues/9464