[DOC] SOR: Kupo startup command is broken

[4TT1L4]

Problem:

• The Kupo startup command examle is broken since a backslash is missing.

Solution:

• Add the missing backslash, so the command could be used as it is in the README.

https://github.com/geniusyield/smart-order-router/blob/230c97969760cb7610c0846688bbe4de5268592c/README.md?plain=1#L190

Resources:

• Reported in comment: https://github.com/geniusyield/smart-order-router/pull/39#issuecomment-1767921843

[4TT1L4]

Fixed in the following PR:

• https://github.com/geniusyield/smart-order-router/pull/39