nei-im/nheko-9999: build is broken, const_lmdb_vals.patch fails to apply

In Nheko a lot of development happened recently. However, this seems to be exclusively in the 0.7.0-dev branch. This version of nheko also seems to depend on the 0.3.0-dev branch of the mtxclient package. It would be nice, if you update the 9999 ebuilds to reflect that.