docs: fix incorrect description in local cache page

Signed-off-by: Sunmin Lee <134378502+sunm2n@users.noreply.github.com>

content/manuals/build/cache/backends/local.md

@@ -1,6 +1,6 @@
 ---
 title: Local cache
-description: Manage build cache with Amazon S3 buckets
+description: Manage build cache with a local directory
 keywords: build, buildx, cache, backend, local
 aliases:
   - /build/building/cache/backends/local/