[1.x][Docs] remove invalid reference in CONVENTIONS.md

Removed missed reference in CONVENTIONS.md.

Issue related:
opensearch-project#1109

Backport PR:
opensearch-project#1110

Signed-off-by: Kawika Avilla <[email protected]>

Author: kavilla

src/core/CONVENTIONS.md

@@ -32,7 +32,7 @@ Definition of done for a feature:
 ## Technical Conventions
 ### Plugin Structure
 
-All OpenSearch Dashboards plugins built at Elastic should follow the same structure.
+All OpenSearch Dashboards plugins should follow the same structure.
 
 ```
 my_plugin/