Rename flag IS_DOGFOOD to IS_STUDIO.

The flag is only set when building from Android Studio... and is never
used for dogfood.

Test: local
Change-Id: I898d585f4558c2437f0152ef102bea59c351f80b
diff --git a/src/com/android/launcher3/CellLayout.java b/src/com/android/launcher3/CellLayout.java
index ac61c49..8718820 100644
--- a/src/com/android/launcher3/CellLayout.java
+++ b/src/com/android/launcher3/CellLayout.java
@@ -538,7 +538,7 @@
         try {
             dispatchRestoreInstanceState(states);
         } catch (IllegalArgumentException ex) {
-            if (FeatureFlags.IS_DOGFOOD_BUILD) {
+            if (FeatureFlags.IS_STUDIO_BUILD) {
                 throw ex;
             }
             // Mismatched viewId / viewType preventing restore. Skip restore on production builds.