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/QueryCopilot/Shared/QueryCopilotClient.ts

@@ -1,7 +1,6 @@
 import { FeedOptions } from "@azure/cosmos";
 import {
   Areas,
-  BackendApi,
   ConnectionStatusType,
   ContainerStatusType,
   HttpStatusCodes,
@@ -32,7 +31,6 @@ import { Action } from "Shared/Telemetry/TelemetryConstants";
 import { traceFailure, traceStart, traceSuccess } from "Shared/Telemetry/TelemetryProcessor";
 import { userContext } from "UserContext";
 import { getAuthorizationHeader } from "Utils/AuthorizationUtils";
-import { useNewPortalBackendEndpoint } from "Utils/EndpointUtils";
 import { queryPagesUntilContentPresent } from "Utils/QueryUtils";
 import { QueryCopilotState, useQueryCopilot } from "hooks/useQueryCopilot";
 import { useTabs } from "hooks/useTabs";
@@ -82,9 +80,7 @@ export const isCopilotFeatureRegistered = async (subscriptionId: string): Promis
 };
 
 export const getCopilotEnabled = async (): Promise<boolean> => {
-  const backendEndpoint: string = useNewPortalBackendEndpoint(BackendApi.PortalSettings)
-    ? configContext.PORTAL_BACKEND_ENDPOINT
-    : configContext.BACKEND_ENDPOINT;
+  const backendEndpoint: string = configContext.PORTAL_BACKEND_ENDPOINT;
 
   const url = `${backendEndpoint}/api/portalsettings/querycopilot`;
   const authorizationHeader: AuthorizationTokenHeaderMetadata = getAuthorizationHeader();