Rendering of markdown agenda has extra spaces at the start

`resolution_fixed` `type_defect`   |    by mt@lowentropy.net

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https://datatracker.ietf.org/doc/agenda-109-sframe/ includes 4 spaces in the <pre> element that includes the document content.

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_Issue migrated from trac:3124 at 2022-03-04 08:05:07 +0000_