delete "other" data from apple watch

You can't really. "Other Data" is system files essentially. If you think other data has grown too large, the only thing you can do is to unpair your watch and set it up again, which you can set from backup. Typically, that will reduce other data. But it will grow again as you use your watch, so unless you are running out of space on your watch, or it is not running well due to low memory, it's usually unnecessary to worry about other data, as it fluctuates.