Backend Migration - Remove Use of Legacy Backend from DE (#2043)

* Default to new backend endpoint if the endpoint in current context does not match existing set in constants.

* Remove some env references.

* Added comments with reasoning for selecting new backend by default.

* Update comment.

* Remove all references to useNewPortalBackendEndpoint now that old backend is disabled in all environments.

* Resolve lint issues.

* Removed references to old backend from Cassandra and Mongo Apis

* fix unit tests

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Co-authored-by: Asier Isayas <aisayas@microsoft.com>

src/Explorer/Tabs/MongoShellTab/getMongoShellUrl.ts

@@ -1,11 +1,11 @@
 import { userContext } from "../../../UserContext";
 
-export function getMongoShellUrl(useMongoProxyEndpoint?: boolean): string {
+export function getMongoShellUrl(): string {
   const { databaseAccount: account } = userContext;
   const resourceId = account?.id;
   const accountName = account?.name;
   const mongoEndpoint = account?.properties?.mongoEndpoint || account?.properties?.documentEndpoint;
   const queryString = `resourceId=${resourceId}&accountName=${accountName}&mongoEndpoint=${mongoEndpoint}`;
 
-  return useMongoProxyEndpoint ? `/mongoshell/index.html?${queryString}` : `/mongoshell/indexv2.html?${queryString}`;
+  return `/mongoshell/index.html?${queryString}`;
 }