verifyJWTClaims fails with single-value aud claim

[osnard]

This one is somehow connected to #333

aud - REQUIRED.
Audience(s) that this ID Token is intended for. It MUST contain the OAuth 2.0 client_id of the Relying Party as an audience value. It MAY also contain identifiers for other audiences. In the general case, the aud value is an array of case sensitive strings. In the special case when there is one audience, the aud value MAY be a single case sensitive string.

See https://openid.net/specs/openid-connect-basic-1_0-29.html#rfc.section.2.2

The current implementation at https://github.com/jumbojett/OpenID-Connect-PHP/blob/v1.0.2/src/OpenIDConnectClient.php#L1205 will break modern PHP versions with

TypeError: in_array(): Argument #2 ($haystack) must be of type array

in case $claims->aud !== $this->clientID but also $claims->aud not being an array.