ci(travis): use `fedora-29` instead of `fedora-30` (for reliability)

[myii]

• Automated using https://github.com/myii/ssf-formula/pull/67

[myii]

Worked first time, as is it's supposed to.

[saltstack-formulas-travis]

:tada: This PR is included in version 0.21.1 :tada:

The release is available on GitHub release

Your semantic-release bot :package::rocket: