fixes typo in package summaries (#2624)

Author: amrit07

docs/package-summary.mdx

@@ -17,7 +17,7 @@ Depends on @emotion/react
 ## @emotion/css
 
 Contains a framework agnostic version of Emotion. Has different functionality and APIs from @emotion/react and doesn’t work the same way under the hood.
-Depends on @emotion/cache which which can be customised by creating a custom instance at @emotion/css/create-instance
+Depends on @emotion/cache which can be customised by creating a custom instance at @emotion/css/create-instance
 
 ## @emotion/cache