Coveralls badge is pointing to old repo

[drcrallen]

As noted in #6007 the coveralls badge points to the old repo via https://coveralls.io/github/druid-io/druid

The new repo would be at https://coveralls.io/repos/apache/incubator-druid but there seem to be some missing settings somewhere. This ask is that the reason be investigated and rectified.

[stale]

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