Update target size docs to call out lifecycle.ignore_changes

[rileykarson]

Addresses yaqs/570067092187906048

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[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

Terraform GA: Diff ( 2 files changed, 6 insertions(+), 4 deletions(-))
Terraform Beta: Diff ( 2 files changed, 6 insertions(+), 4 deletions(-))
TF Conversion: Diff ( 2 files changed, 3 insertions(+), 3 deletions(-))