Remove obsolete mx_InviteDialog_transferButton class (#10687)

The class has been introduced by 2cc6bce ("Much theming & visual of transfer window dial pad"), and removed by c829cb9 ("Use flexbox to layout buttons") from _InviteDialog.scss on the same PR. The class has not used anywhere else since then.

Signed-off-by: Suguru Hirahara <[email protected]>

src/components/views/dialogs/InviteDialog.tsx

@@ -1433,7 +1433,6 @@ export default class InviteDialog extends React.PureComponent<Props, IInviteDial
                     <AccessibleButton
                         kind="primary"
                         onClick={this.transferCall}
-                        className="mx_InviteDialog_transferButton"
                         disabled={!hasSelection && this.state.dialPadValue === ""}
                     >
                         {_t("Transfer")}