cleanup: Removes the user-agent string from presence (unused).

modules/xmpp/ChatRoom.js

         this.presMap.to = this.myroomjid;
         this.presMap.xns = 'http://jabber.org/protocol/muc';
         this.presMap.nodes = [];
-        this.presMap.nodes.push({
-            'tagName': 'user-agent',
-            'value': navigator.userAgent,
-            'attributes': { xmlns: 'http://jitsi.org/jitmeet/user-agent' }
-        });
 
         if (options.enableStatsID) {
             this.presMap.nodes.push({

modules/xmpp/ChatRoom.spec.js

                 to: 'tojid',
                 from: 'fromjid'
             })
-            .c('user-agent').t('user-agent-text').up();
+            .c('element-name').t('element-name-text').up();
 
             parser.packet2JSON(p.tree(), nodes);
 
             expect(nodes.length).toBe(1);
-            const userAgent = nodes.find(n => n.tagName === 'user-agent');
+            const elem = nodes.find(n => n.tagName === 'element-name');
 
-            expect(userAgent).toBeTruthy();
-            expect(Object.keys(userAgent.attributes).length).toEqual(0);
-            expect(userAgent.children.length).toEqual(0);
-            expect(userAgent.value).toEqual('user-agent-text');
+            expect(elem).toBeTruthy();
+            expect(Object.keys(elem.attributes).length).toEqual(0);
+            expect(elem.children.length).toEqual(0);
+            expect(elem.value).toEqual('element-name-text');
         });
 
         it('translates elements with children correctly', () => {