[memcached] Removed groupId (duplicates parent).
[memcached] Removed groupId (duplicates parent).

For reference, other bindings don't appear to specify a `groupId` at this level
in their `pom.xml` files.

@shivam-maharshi says in a [comment][1]:

> The groupId here is the duplicate of the parent groupId. This is creating a
> problem in the maven build.

  [1]: https://github.com/brianfrankcooper/YCSB/commit/d4b1d247a31cf9fbf42b2e324b5b1cc27fdd9565#commitcomment-15030853

madhurihn/YCSB_ToyDB,zyguan/ycsb,leschekhomann/YCSB,leschekhomann/YCSB,cricket007/YCSB,ChristianNavolskyi/YCSB,zyguan/ycsb,leschekhomann/YCSB,ChristianNavolskyi/YCSB,madhurihn/YCSB_ToyDB,jaemyoun/YCSB,brianfrankcooper/YCSB,manolama/YCSB,ChristianNavolskyi/YCSB,jaemyoun/YCSB,brianfrankcooper/YCSB,manolama/YCSB,jaemyoun/YCSB,ChristianNavolskyi/YCSB,zyguan/ycsb,madhurihn/YCSB_ToyDB,zyguan/ycsb,cricket007/YCSB,brianfrankcooper/YCSB,manolama/YCSB,manolama/YCSB,madhurihn/YCSB_ToyDB,brianfrankcooper/YCSB,cricket007/YCSB,cricket007/YCSB,jaemyoun/YCSB,leschekhomann/YCSB