docs: fix image link

Signed-off-by: Ben Iofel <[email protected]>

docs/trace-prefetch.md

@@ -1,6 +1,6 @@
 ## Prefetch - Overview
 
-Cache has been playing an important role in the whole architecture of ACI's [I/O flow](docs/images/image-flow.jpg "image data flow"). When there is no cache (container cold start), however, the backend storage engine will still need to visit Registry frequently, and temporarily.
+Cache has been playing an important role in the whole architecture of ACI's [I/O flow](images/image-flow.jpg "image data flow"). When there is no cache (container cold start), however, the backend storage engine will still need to visit Registry frequently, and temporarily.
 
 Prefetch is a common mechanism to avoid this situation. As it literally suggests, the key is to retrieve data in advance, and save them into cache.
 
@@ -68,4 +68,4 @@ Measure the service available time (in seconds) of a Wordpress container. The te
 | | **With cache** | **Without cache (cold start)** |
 | :----: | :----: | :----: |
 | **With trace prefetch** | 4.981s | 15.253s |
-| **Without trace prefetch** | 5.259s | 60.511s |
+| **Without trace prefetch** | 5.259s | 60.511s |