Log Message:
textproc/ruby-kramdown-rfc2629: update to 1.3.31

pkgsrc change: remove unnecessary OVERRIDE_GEMSPEC.

1.3.31 (2021-02-13)

* Add temporary workaround for draft referencing regression

1.3.30 (2021-02-12)

* Use rfc-editor/datatracker for RFC/I-D bibxml unless
  KRAMDOWN_USE_TOOLS_SERVER environment variable is set.

1.3.29 (2021-02-12)

* Do not use server-side anchor setup for stand_alone: true

1.3.28 (2021-02-05)

* SVG error handling fixes