Add requires on php-process

Without this package, occ refuse to work. 
# php /usr/share/nextcloud/occ
The posix extensions are required - see http://php.net/manual/en/book.posix.php

nextcloud.spec

@@ -78,6 +78,7 @@ Requires:       php-ldap
 Requires:       php-smbclient
 Requires:       php-imap
 Requires:       php-gmp
+Requires:       php-process
 Requires:       php-pecl-imagick
 Requires:       php-pecl-memcached
 Requires:       php-pecl-apcu