[MINOR] docs: Fix the description of Multi-engine support in `overv…

…iew.md` (apache#6439)

### What changes were proposed in this pull request?
This PR fixes the description of the `Multi-engine support` section in
`overview.md`, as Gravitino now supports connectors for Apache Spark and
Apache Flink.

### Why are the changes needed?
Gravitino now supports connectors for Apache Spark and Apache Flink.


### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?
manual review

docs/overview.md

@@ -60,8 +60,9 @@ Gravitino supports different query engines to access the metadata. Currently, it
 [Trino](https://trino.io/), users can use Trino to query the metadata and data without needing to
 change the existing SQL dialects.
 
-In the meantime, other query engine support is on the roadmap, including
-[Apache Spark](https://spark.apache.org/), [Apache Flink](https://flink.apache.org/) and others.
+In addition, Gravitino has expanded its support to include [Apache Spark](https://spark.apache.org/)
+and [Apache Flink](https://flink.apache.org/), among other query engines. Further enhancements and
+additions to the supported query engines are also on the roadmap.
 
 ### AI asset management