Probably ought to update TestIndexFixtures

`TestIndexFixtures` is currently using version 2.3.0 of the data set:

https://github.com/ssbc/go-ssb/blob/d94e3c8180aa0f021eb22bcb963d3478259e2c80/multilogs/integration_prep.bash#L17

Current release version at the time of filing this issue is 3.0.2:

https://github.com/ssbc/ssb-fixtures/releases/tag/3.0.2