source: replace weak signing key
source: replace weak signing key

There is a case that verifying source archive causes invalid key error
when source archive is signed with weak (dsa1024) signing key.

kenhys/groonga,naoa/groonga,naoa/groonga,naoa/groonga,komainu8/groonga,naoa/groonga,groonga/groonga,groonga/groonga,kenhys/groonga,groonga/groonga,naoa/groonga,kenhys/groonga,komainu8/groonga,kenhys/groonga,komainu8/groonga,naoa/groonga,groonga/groonga,kenhys/groonga,komainu8/groonga,groonga/groonga,naoa/groonga,komainu8/groonga,kenhys/groonga,groonga/groonga,komainu8/groonga,kenhys/groonga,naoa/groonga,komainu8/groonga,komainu8/groonga,groonga/groonga,groonga/groonga,kenhys/groonga