fix(sdk-core): update the staging Environment

- uses the correct urls for newly provisioned staging environment

Ticket: BG-59878

Author: sumanmukherjee03

modules/bitgo/test/unit/bitgo.ts

@@ -52,7 +52,7 @@ describe('BitGo Prototype Methods', function () {
     it('staging', () => {
       BitGoJS.setNetwork('testnet');
       TestBitGo.decorate(BitGo, { env: 'staging' });
-      BitGoJS.getNetwork().should.equal('bitcoin');
+      BitGoJS.getNetwork().should.equal('testnet');
     });
 
     it('test', () => {

modules/sdk-core/src/bitgo/environments.ts

@@ -155,9 +155,9 @@ export const Environments: Environments = {
     uri: 'https://app.bitgo-latest.com',
     stellarFederationServerUrl: 'https://app.bitgo-latest.com/api/v2/xlm/federation',
   }),
-  staging: Object.assign({}, mainnetBase, {
-    uri: 'https://staging.bitgo.com',
-    stellarFederationServerUrl: 'https://staging.bitgo.com/api/v2/xlm/federation',
+  staging: Object.assign({}, testnetBase, {
+    uri: 'https://app.bitgo-staging.com',
+    stellarFederationServerUrl: 'https://app.bitgo-staging.com/api/v2/txlm/federation',
   }),
   local: Object.assign({}, devBase, {
     uri: 'https://localhost:3000',