docs: update Angular Global Summit on event pages (#41050)

After my speaker meeting with the Geekle team, they communicated that
they moved the date to avoid colliding with ng-conf. Originally added
in#40697, per @mgechev.

PR Close #41050

aio/content/marketing/events.json

@@ -1,4 +1,13 @@
 [
+  {
+    "name": "Angular Global Summit",
+    "location": "Online",
+    "linkUrl": "https://link.geekle.us/angular/offsite",
+    "date": {
+      "start": "2021-06-01",
+      "end": "2021-06-02"
+    }
+  },
   {
     "name": "ng-conf",
     "location": "Online",
@@ -12,15 +21,6 @@
       "end": "2021-04-15"
     }
   },
-  {
-    "name": "Angular Global Summit",
-    "location": "Online",
-    "linkUrl": "https://angular.geekle.us/",
-    "date": {
-      "start": "2021-04-13",
-      "end": "2021-04-14"
-    }
-  },
   {
     "name": "ng-china",
     "location": "Online",