Rename Group icon to People, and add high detail variant

The icon is called People in the UX team's icon system, and we need to stay aligned to that.
The high detail variant has an extra person in it.

Contributes to issue CURA-8530.

resources/qml/WelcomePages/CloudContent.qml

@@ -172,7 +172,7 @@ Item
                         anchors.horizontalCenter: communityColumn.horizontalCenter
                         fillMode: Image.PreserveAspectFit
                         width: UM.Theme.getSize("welcome_wizard_cloud_content_image").width
-                        source: UM.Theme.getIcon("Group", "high")
+                        source: UM.Theme.getIcon("People", "high")
                         sourceSize.width: width
                         sourceSize.height: height
                     }

resources/themes/cura-light/icons/deprecated_icons.json

@@ -332,7 +332,7 @@
         "size": "default"
     },
     "group": {
-        "new_icon": "Group",
+        "new_icon": "People",
         "size": "default"
     },
     "link": {