Correctly indent default configs in newrelic.yml template

[oboxodo]

This is so that uncommenting any of these options and setting a value will be correctly included in the common: &default_settings block. I discovered this while investigating #731 (comment).

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[fallwith]

@oboxodo thank you so much for noticing this and submitting the fix! This will surely help lots of others in the future. We appreciate your contribution!