replace deprecated setDataSource by setRpcEndpoint

src/processor.ts

-import { assertNotNull } from '@subsquid/util-internal'
 import {
     BlockHeader,
     DataHandlerContext,
     SubstrateBatchProcessor,
     SubstrateBatchProcessorFields,
-    Event as _Event,
     Call as _Call,
+    Event as _Event,
     Extrinsic as _Extrinsic
 } from '@subsquid/substrate-processor'
+import { assertNotNull } from '@subsquid/util-internal'
 
 export const processor = new SubstrateBatchProcessor()
-    .setDataSource({
+    .setRpcEndpoint(
         // Lookup archive by the network name in Subsquid registry
         // See https://docs.subsquid.io/substrate-indexing/supported-networks/
         // archive: lookupArchive('gdev', {genesis: '0xc2347f3d89dc190608abe2e09311c10dc1b3fd9555935ef994ac93c5f279a857'}),
         // Chain RPC endpoint is required on Substrate for metadata and real-time updates
-        chain: {
+        {
             // Set via .env for local runs or via secrets when deploying to Subsquid Cloud
             // https://docs.subsquid.io/deploy-squid/env-variables/
             url: assertNotNull(process.env.RPC_ENDPOINT),
             // More RPC connection options at https://docs.subsquid.io/substrate-indexing/setup/general/#set-data-source
             // rateLimit: 10
-        }
         })
     .addEvent({
         // name: [],