Update CI for Polkadot People Chain

[joepetrowski]

The People Chain is now live (here's one endpoint). Therefore, CI should start fetching GitHub handles from the People Chain.

Note that GitHub handles are now first-class fields of the Identity and that Identities with { "github" : "mygithubname" } have been migrated to the new data structure. As in, for example:

[
  {
    judgements: [
      [
        0
        Reasonable
      ]
    ]
    deposit: 203,240,000,000
    info: {
      additional: [
        [
          {
            Raw: github
          }
          {
            Raw: joepetrowski
          }
        ]
      ]
      display: {
        Raw: Joe
      }
      legal: {
        Raw: Joe Petrowski
      }
      web: None
      riot: None
      email: {
        Raw: joe@petrow.ski
      }
      pgpFingerprint: null
      image: None
      twitter: None
    }
  }
  null
]

Becomes:

[
  {
    judgements: [
      [
        0
        Reasonable
      ]
    ]
    deposit: 0
    info: {
      display: {
        Raw: Joe
      }
      legal: {
        Raw: Joe Petrowski
      }
      web: None
      matrix: None
      email: {
        Raw: joe@petrow.ski
      }
      pgpFingerprint: null
      image: None
      twitter: None
      github: {
        Raw: joepetrowski
      }
      discord: None
    }
  }
  null
]

(Also note that riot has changed to matrix.)

The switch should happen prior to 25 July, when ref 983 enacts. At this point, identities can start being removed from the Relay Chain, so it will no longer be a reliable source of the information.

CC @pepoviola @mordamax

[pepoviola]

Cc @Bullrich

[josepot]

The People Chain is now live (here's one endpoint). Therefore, CI should start fetching GitHub handles from the People Chain.

FWIW the chain-spec of the Polkadot People Chain is nowhere to be found.