remove aggregate from feedback

[ukclivecox]

What this PR does / why we need it:

• Removes the incorrect call to aggregate as part of feedback children processing

Which issue(s) this PR fixes:

Fixes #3139

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[seldondev]

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[ukclivecox]

/test notebooks

[ukclivecox]

/test integration

[axsaucedo]

/test notebooks