Update moving-to-federation-2.mdx (#3121)

Changed 

"The schema changes you make are backward incompatible with Federation
1..."

TO 

"The schema changes you make are not backward compatible with Federation
1..."

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docs/source/federation-2/moving-to-federation-2.mdx

@@ -172,7 +172,7 @@ Federation 2 provides powerful new features that require making some changes to
 - Safely migrating fields from one subgraph to another with [`@override`](../federated-types/federated-directives#override)
 - Hiding internal routing fields from graph consumers with [`@inaccessible`](../federated-types/federated-directives#inaccessible)
 
-The schema changes you make are backward incompatible with Federation 1, which means you won't be able to use Federation 1 composition anymore unless you revert those changes.
+The schema changes you make are not backward compatible with Federation 1, which means you won't be able to use Federation 1 composition anymore unless you revert those changes.
 
 ### Update your subgraph library