fix code style

src/php/lib/Grpc/AbstractCall.php

src/php/lib/Grpc/BaseStub.php

src/php/lib/Grpc/BidiStreamingCall.php

src/php/lib/Grpc/ClientStreamingCall.php

src/php/lib/Grpc/ServerStreamingCall.php

src/php/lib/Grpc/UnaryCall.php