effects/overview: enable it by default

Overview is quite polished now, enough that we have a default touchpad
gesture that opens it by default. It's time to move it out of public
beta and enable it by default, and this commit does that.

BUG: 446753
FIXED-IN: 5.25

src/effects/overview/metadata.json

@@ -32,7 +32,7 @@
         "Description[vi]": "Cho phép bạn xem tổng quan các bàn làm việc ảo và các cửa sổ",
         "Description[x-test]": "xxAllows you to overview virtual desktops and windowsxx",
         "Description[zh_CN]": "显示包含当前所有虚拟桌面和窗口的桌面概览",
-        "EnabledByDefault": false,
+        "EnabledByDefault": true,
         "Id": "overview",
         "License": "GPL",
         "Name": "Overview",