test: Update Jest snapshots and reference the 6.0 index

The integration test on master is reference 7.0 because it aims
toward helping users migrate from 7.0 -> 8.0. The 7.x branch
is running 6.0 data as it helps migrate from older indices.

x-pack/test/upgrade_assistant_integration/upgrade_assistant/status.ts

@@ -15,26 +15,26 @@ export default function({ getService }: FtrProviderContext) {
 
   describe('status and _cluster/state contract', () => {
     beforeEach(async () => {
-      await es.indices.open({ index: '7.0-data' });
+      await es.indices.open({ index: '6.0-data' });
     });
 
     afterEach(async () => {
-      await es.indices.open({ index: '7.0-data' });
+      await es.indices.open({ index: '6.0-data' });
     });
 
     // According to https://www.elastic.co/guide/en/elasticsearch/reference/7.6/cluster-state.html
     // The response from this call is considered internal and subject to change. We check that
     // the contract has not changed in this integration test.
     it('the _cluster/state endpoint is still what we expect', async () => {
       await esArchiver.load('upgrade_assistant/reindex');
-      await es.indices.close({ index: '7.0-data' });
+      await es.indices.close({ index: '6.0-data' });
       const result = await es.cluster.state({
-        index: '7.0-data',
+        index: '6.0-data',
         metric: 'metadata',
       });
 
       try {
-        if (getIndexStateFromClusterState('7.0-data', result.body) === 'close') {
+        if (getIndexStateFromClusterState('6.0-data', result.body) === 'close') {
           return;
         }
       } catch (e) {
@@ -50,7 +50,7 @@ export default function({ getService }: FtrProviderContext) {
           2
         )}.
 
-Expected body.metadata.indices['7.0-data'].state to be "close".`
+Expected body.metadata.indices['6.0-data'].state to be "close".`
       );
     });
   });