QA stats aggregation: exclude isFile / isError pages from stats (#1879)

Follow-up to: #1868, exclude pages that have isFile or isError set to
true from the stats aggregation.

backend/btrixcloud/pages.py

@@ -577,7 +577,13 @@ class PageOps:
             boundaries.append(1.1)
 
         aggregate = [
-            {"$match": {"crawl_id": crawl_id}},
+            {
+                "$match": {
+                    "crawl_id": crawl_id,
+                    "isFile": {"$ne": True},
+                    "isError": {"$ne": True},
+                }
+            },
             {
                 "$bucket": {
                     "groupBy": f"$qa.{qa_run_id}.{key}",