Make show_on... fields boolean

At least the documentation reads as if they are boolean.

Change-Id: Ie4d2021825feaf42612481fa0727cd9f3c22dbc5
diff --git a/polygerrit-ui/app/types/common.ts b/polygerrit-ui/app/types/common.ts
index 434a9ad..a3104ac 100644
--- a/polygerrit-ui/app/types/common.ts
+++ b/polygerrit-ui/app/types/common.ts
@@ -1327,8 +1327,8 @@
   name: string;
   url: string;
   image_url: string;
-  show_on_side_by_side_diff_view: string;
-  show_on_unified_diff_view: string;
+  show_on_side_by_side_diff_view: boolean;
+  show_on_unified_diff_view: boolean;
 }
 
 /**