fix infura rpc detection

[legobeat]

Fixes the following error when trying to connect to Rinkeby:

backend.js:12979 Warning: Failed prop type: Invalid prop `showDeprecatedRpcUrlWarning` of type `array` supplied to `LoadingNetworkScreen`, expected `boolean`.
    in LoadingNetworkScreen (created by ConnectFunction)
    in ConnectFunction (created by Routes)
    in div (created by Routes)
    in div (created by Routes)
    in Routes (created by ConnectFunction)
    in ConnectFunction (created by Context.Consumer)
    in withRouter(Connect(Routes)) (created by Index)
    in LegacyI18nProvider (created by Index)
    in I18nProvider (created by Index)
    in LegacyMetaMetricsProvider (created by Index)
    in MetaMetricsProvider (created by Index)
    in Router (created by HashRouter)
    in HashRouter (created by Index)
    in Provider (created by Index)
    in Index

Also actually check the domain rather than substring inclusion on the URL.

[github-actions]

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[Gudahtt]

LGTM!