Remove check for the ClientCredentials storage type because grant types that uses ClientAssertionType does not require it.
Remove check for the ClientCredentials storage type because grant types that uses ClientAssertionType does not require it.

huxingbang/oauth2-server-php,rakesh-mohanta/oauth2-server-php,continuousphp/oauth2-server-php,EricFu728/oauth2-server-php,digitalliving/oauth2-server-php,sariabod/oauth2-server-php,eric-admin/oauth,phindmarsh/oauth2-server-php,falconeric/oauth2-server-php,philip8728/oauth2-server-php,eric-admin/oauth2-server-php,coolcodechick/oAuth2,Peercraft/oauth2-server-php,wkstar/oauth2-server-php,qycloud/oauth,winlolo/oauth2-server-php,Wilt/oauth2-server-php,kazitanvirahsan/oauth2-server-php,tobias74/oauth2-server-php,svycka/oauth2-server-php,m3kan1cal/oauth2-server-php,anek77713/oauth2-server-php,bshaffer/oauth2-server-php,jahanzaibbahadur/oauth2-server-php,mojaray2k/oauth2-server-php,xuwenzhi/oauth2-server-php,PortNumber53/oauth2-server-php,continuousphptest/oauth2-server-php,akash1808/oauth2-server-php,mondor/oauth2-server-php,Alex-Zaharow/oauth20-server01,MattermarkStudios/oauth2-server-php,vitapublic/oauth2-server-php,wesleywillians/oauth2-server-php,masiac/my-oauth2-server-php,SixSrt/oauth2-server-php,wanadev/oauth2-server-php,EhteshamMehmood/oauth2-server-php,copynpaste/oauth2-server-php,jniebuhr/oauth2-server-php