renaming PHPCRMenuProvider to PhpcrMenuProvider

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | https://github.com/symfony-cmf/symfony-cmf-docs/commit/4b0c4cf7723af2e34b509b8d623231eb6353f560

according to CS.