Update screenshot shelf UI flag name

Flipping the old flag turned it on in old builds (where the
experience is not ready yet); changing the flag name and re-rolling it
out.

Bug: 329659738
Flag: NONE
(changes now flagged under com.android.systemui.screenshot_shelf_ui2)
Test: manual (device with the old flag has the old UI; flipping the new
flag gets the new (and not broken) UI)

Change-Id: I8250035bf8d33b977088a7aa748d780de306a7e0
diff --git a/packages/SystemUI/aconfig/systemui.aconfig b/packages/SystemUI/aconfig/systemui.aconfig
index e38f347..fadef1e 100644
--- a/packages/SystemUI/aconfig/systemui.aconfig
+++ b/packages/SystemUI/aconfig/systemui.aconfig
@@ -497,7 +497,7 @@
 }
 
 flag {
-    name: "screenshot_shelf_ui"
+    name: "screenshot_shelf_ui2"
     namespace: "systemui"
     description: "Use new shelf UI flow for screenshots"
     bug: "329659738"