Rename "memcache" to "memcached"

[tbreuss]

Rename "memcache" to "memcached", as the install instructions refer to the latter, which is kind of confusing (since memcache != memcached).

[what-the-diff[bot]]

PR Summary

• Updated section title and content Changed the title of a section from "memcache" to "memcached" and updated all instances within that section to maintain consistency.

[schmunk42]

Thank you!