Remove regexp exploit

[strider2038]

https://github.com/strider2038/imgcache-service/blob/8ec28b28ddad1c228a91592a7c937963a28fdad5/src/Service/Router.php#L116

(...+...)* might be exploited (ReDoS, Regular Expression Denial of Service)

[strider2038]

Not actual (validations moved to Symfony validation, source of strings is configuration, not web)