Broken Link on Cache Design article

[pjambet]

The link to https://github.com/dragonflydb/dragonfly/blob/main/docs/dashtable.md on https://dragonflydb.io/blog/2022/06/23/cache_design/ is broken, it points to https://github.com/dragonflydb/dragonfly/blob/main/doc/dashtable.md, missing s on docs