Display message if not mainnet (#3151)

src/components/vote/ProposalEmptyState.tsx

 import { Trans } from '@lingui/macro'
-import { L2_CHAIN_IDS } from 'constants/chains'
+import { SupportedChainId } from 'constants/chains'
 import useActiveWeb3React from 'hooks/useActiveWeb3React'
 import styled from 'styled-components/macro'
 import { ThemedText } from 'theme'
@@ -38,7 +38,7 @@ const EmptyState = ({ HeaderContent, SubHeaderContent }: EmptyStateProps) => (
 
 export default function ProposalEmptyState() {
   const { chainId } = useActiveWeb3React()
-  if (chainId && L2_CHAIN_IDS.includes(chainId)) {
+  if (chainId && chainId !== SupportedChainId.MAINNET) {
     return (
       <EmptyState
         HeaderContent={() => <Trans>Please connect to Layer 1 Ethereum</Trans>}