adopters: add zhihu case study

Signed-off-by: Ran <huangran@pingcap.com>

adopters.md

@@ -28,7 +28,7 @@ This is a list of TiDB adopters in various industries.
 |[Youju Tech](https://nn.yjyz.com/)|E-commerce||
 |[Maizuo](https://www.crunchbase.com/organization/maizhuo)|E-commerce||
 |[Mogujie](https://www.crunchbase.com/organization/mogujie)|E-commerce||
-|[Zhihu](https://en.wikipedia.org/wiki/Zhihu)|Knowledge Sharing|English [#1](https://pingcap.com/case-studies/lesson-learned-from-queries-over-1.3-trillion-rows-of-data-within-milliseconds-of-response-time-at-zhihu/), [#2](https://pingcap.com/case-studies/horizontally-scaling-hive-metastore-database-by-migrating-from-mysql-to-tidb); [Chinese](https://pingcap.com/cases-cn/user-case-zhihu/)|
+|[Zhihu](https://en.wikipedia.org/wiki/Zhihu)|Knowledge Sharing|English [#1](https://pingcap.com/case-studies/lesson-learned-from-queries-over-1.3-trillion-rows-of-data-within-milliseconds-of-response-time-at-zhihu/), [#2](https://pingcap.com/case-studies/horizontally-scaling-hive-metastore-database-by-migrating-from-mysql-to-tidb), [#3](https://pingcap.com/case-studies/boosting-big-data-performance-by-combining-tidb-with-hive-and-hdfs); [Chinese](https://pingcap.com/cases-cn/user-case-zhihu/)|
 |[PatSnap](https://www.crunchbase.com/organization/patsnap)|Artificial Intelligence| [English](https://pingcap.com/case-studies/why-we-chose-a-scale-out-data-warehouse-for-real-time-analytics); [Chinese](https://pingcap.com/cases-cn/user-case-zhihuiya/)|
 |[JD Cloud](https://www.crunchbase.com/organization/jd-cloud)|Cloud Computing|[English](https://pingcap.com/case-studies/lesson-learned-from-40-k-qps-and-20-billion-rows-of-data-in-a-single-scale-out-cluster/); [Chinese](https://pingcap.com/cases-cn/user-case-jingdongyun/)|
 |[Mobike](https://en.wikipedia.org/wiki/Mobike)|Ridesharing|[English](https://pingcap.com/case-studies/tidb-in-mobike); Chinese [#1](https://pingcap.com/cases-cn/user-case-mobike/), [#2](https://pingcap.com/cases-cn/user-case-mobike-2/)|