fixed skip.js - fixed a embed error message

[RJ1002]

Please describe the changes this PR makes and why it should be merged:

fixed the message: There is nothing after [${song.title}](${song.uri}) in the queue. now it will send a message if there is only one song playing.

Before: After:

Status and versioning classification:

Important.

• Write in camelCase, not snake_case.
• Do not push to master/main without testing your changes first, make a branch if you have to.

[RJ1002]

there is a better way to fix this in #192