Update proposals/propertyDependencies.md

Co-authored-by: Greg Dennis <[email protected]>

Author: jdesrosiers

proposals/propertyDependencies.md

@@ -44,7 +44,7 @@ significant [problems](#problems).
 
 OpenAPI solves this problem with the `discriminator` keyword. However, their
 approach is more oriented toward code generation concerns, is poorly specified
-when it comes to validation, and is couple to OpenAPI concepts that don't exist
+when it comes to validation, and is coupled to OpenAPI concepts that don't exist
 is JSON Schema. Therefore, it's necessary to define something new rather than
 adopt `discriminator`.