[ExpressionLanguage] replaced the =~ operator by matches (removed the != operator)

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

To be consistent with fabpot/Twig#1209