docs: Update performance.mdx

Author: igorlukanin

docs/pages/product/workspace/performance.mdx

@@ -71,7 +71,7 @@ using pre-aggregations:
 
 <Screenshot src="https://ucarecdn.com/fe784a74-edd5-44c0-803f-267237219b1d/"/>
 
-The&nbsp;<Btn>Avg. response time by data source</Btn> shows the difference
+The&nbsp;<Btn>Avg. response time by cache type</Btn> shows the difference
 in the response time for requests that hit pre-aggregations, in-memory cache,
 or no cache (i.e., the upstream data source). The next chart shows that
 pre-aggregations usually provide sub-second response times while queries to