Fix clippy warnings

core/storage/page_cache.rs

@@ -843,10 +843,6 @@ mod tests {
         key
     }
 
-    fn page_has_content(page: &PageRef) -> bool {
-        page.is_loaded() && page.get().contents.is_some()
-    }
-
     fn insert_and_get_entry(cache: &mut PageCache, id: usize) -> (PageCacheKey, PageCacheEntry) {
         let key = create_key(id);
         let page = page_with_content(id);

core/storage/pager.rs

@@ -2423,7 +2423,7 @@ mod tests {
             })
         };
         let _ = thread.join();
-        let mut cache = cache.write();
+        let cache = cache.read();
         let page_key = PageCacheKey::new(1);
         let page = cache.get(&page_key).unwrap();
         assert_eq!(page.unwrap().get().id, 1);