When generating multi-part upload IDs remove `/` characters (#3164)
When generating multi-part upload IDs remove `/` characters (#3164)

* / are not allowed in upload ids

* ran black
william-richard/moto,spulec/moto,william-richard/moto,spulec/moto,william-richard/moto,william-richard/moto,spulec/moto,william-richard/moto,spulec/moto,william-richard/moto,spulec/moto,spulec/moto