Clarify the license of erb

[k0kubun]

ref: https://github.com/ruby/resolv/issues/45

[k0kubun]

Patch authors since https://github.com/ruby/erb/commit/86e24c83f5293e6c1f8bdb210b43e831b2c87bff:

$ git shortlog -sn 86e24c83f5293e6c1f8bdb210b43e831b2c87bff..
    76  Takashi Kokubun
    15  Hiroshi SHIBATA
     2  dependabot[bot]
     1  Jean Boussier
     1  Josh Nichols
     1  Kenichi Kamiya
     1  Lars Kanis
     1  Nobuyoshi Nakada
     1  b-sakata
     1  ooooooo_q

@hsbt @byroot @technicalpickles @kachick @larskanis @nobu @b-sakata @ooooooo-q If you object to including Ruby's License, could you mention it here by 2024-06-01 00:00:00 UTC? Just add a :+1: reaction if you have no objection.

[k0kubun]

Given that @nobu and @b-sakata didn't reply in time, I assume they have no objection to the change. Everybody else has made an explicit :+1: reaction (image attached for the record).