Stop using deprecated methods, fields & exports (#12524)

* Remove legacy `threepidCreds` field

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Remove `user` field legacy UIA fallback

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Update imports

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

* Fix test

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

---------

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

src/components/views/dialogs/security/CreateCrossSigningDialog.tsx

@@ -101,9 +101,6 @@ export default class CreateCrossSigningDialog extends React.PureComponent<IProps
                     type: "m.id.user",
                     user: MatrixClientPeg.safeGet().getUserId(),
                 },
-                // TODO: Remove `user` once servers support proper UIA
-                // See https://github.com/matrix-org/synapse/issues/5665
-                user: MatrixClientPeg.safeGet().getUserId(),
                 password: this.state.accountPassword,
             });
         } else if (this.props.tokenLogin) {