fix(tsdb/cache): use 5M cache for block index instead of 1M

source/dnode/vnode/src/tsdb/tsdbCache.c

@@ -17,7 +17,7 @@
 
 static int32_t tsdbOpenBICache(STsdb *pTsdb) {
   int32_t    code = 0;
-  SLRUCache *pCache = taosLRUCacheInit(1 * 1024 * 1024, -1, .5);
+  SLRUCache *pCache = taosLRUCacheInit(5 * 1024 * 1024, -1, .5);
   if (pCache == NULL) {
     code = TSDB_CODE_OUT_OF_MEMORY;
     goto _err;