Fixes invalid value for ddl-auto in sagan-site

Change spring.jpa.hibernate.ddl-auto from 'false' (invalid) to 'none' in sagan-site. This was previously fixed in sagan-indexer (see #365), but missed this one.
Merge pull request #383 from bjornerik/fix-ddl-auto2

Fixes invalid value for ddl-auto in sagan-site