best-practices: removed extra article

Author: nathan-websculpt

website/src/pages/en/subgraphs/querying/best-practices.mdx

@@ -364,7 +364,7 @@ When using the types generation tool, the above query will generate a proper `De
 
 ### Dos and Don'ts for Fragments
 
-1. Fragments cannot be based on a non-applicable types (types without fields).
+1. Fragments cannot be based on non-applicable types (types without fields).
 2. `BigInt` cannot be used as a fragment's base because it's a **scalar** (native "plain" type).
 
 Example: