Table IHeaderRow interface changed type

[dlabrecq]

It appears we changed an interface when introducing linting to the react-table package. This is exported, so likely a breaking change.

https://github.com/patternfly/patternfly-react/pull/3693/files#diff-9bda7132cc01104382345447864888d5L64

Thinking this change should be reverted and wait for the table's breaking changes PR #3296?