:bug: fix: remove trailing whitespace in readme gen

[bzub]

trafficstars

This should help users start out with a README that avoids trailing whitespaces.

Fixes: https://github.com/kubernetes-sigs/kubebuilder/issues/3812

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This pull-request has been approved by: bzub, camilamacedo86, mateusoliveira43

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[bzub]

/retest