One of Dorchester’s longstanding pizza and sub spots has closed its doors— apparently for good. The space at formerly housed Venice Pizza at the corner of Dot Ave and Savin Hill Ave is now “available for lease,” according to signage that was posted in its windows last week. The restaurant closed earlier in the year. The 2,117 sq. ft. storefront at 39 Savin Hill Ave. is being marketed by Boston Realty Advisors.