doc: move translations kcm to plasma-workspace as well

at time of moving, index.docbook was at commit,

c1b9e8003febb1da46b110ff7a92e5b4e036b732

and plasma-desktop head was at,

6eb2d544c767d49b9dfc3dc8f5f1b5b26912f8ca

Removed in commit,

ced62362743e113813e5e8d9cc292c88be413875

CCMAIL: Burkhard Lück <lueck@hube-lueck.de>