main: clean cache by atime

src/main/api/cache.js

@@ -73,7 +73,7 @@ class Cache {
         let diskUsage = stats.reduce((x, y)=> x + y.size, 0);
         if (diskUsage <= this.cacheLimit)
             return;
-        stats.sort((a, b)=> a.ctime < b.ctime);
+        stats.sort((a, b)=> a.atime < b.atime);
         for (const st of stats) {
             const size = st.size;
             diskUsage -= size;