remove pre-4.2 logic in sessions

Author: dariakp

src/sessions.ts

@@ -42,7 +42,6 @@ import {
   commandSupportsReadConcern,
   isPromiseLike,
   List,
-  maxWireVersion,
   MongoDBNamespace,
   noop,
   now,
@@ -51,8 +50,6 @@ import {
 } from './utils';
 import { WriteConcern, type WriteConcernOptions, type WriteConcernSettings } from './write_concern';
 
-const minWireVersionForShardedTransactions = 8;
-
 /** @public */
 export interface ClientSessionOptions {
   /** Whether causal consistency should be enabled on this session */
@@ -405,17 +402,6 @@ export class ClientSession
       this.unpin();
     }
 
-    const topologyMaxWireVersion = maxWireVersion(this.client.topology);
-    if (
-      isSharded(this.client.topology) &&
-      topologyMaxWireVersion != null &&
-      topologyMaxWireVersion < minWireVersionForShardedTransactions
-    ) {
-      throw new MongoCompatibilityError(
-        'Transactions are not supported on sharded clusters in MongoDB < 4.2.'
-      );
-    }
-
     this.commitAttempted = false;
     // increment txnNumber
     this.incrementTransactionNumber();