Update CONTRIBUTING.md

Co-authored-by: Krzysztof Findeisen <[email protected]>

CONTRIBUTING.md

@@ -53,7 +53,7 @@ Schema Versioning Overview
 --------------------------
 
 Individual schemas may have their own internal [version](https://felis.lsst.io/user-guide/model.html#schema-version) for tracking changes, which is defined at the top level of the file, as in [apdb.yaml](yml/apdb.yaml).
-(This is distinct from tags or versions of sdm_schemas itself, and not all schemas may be using these internal versions.)
+(This is distinct from tags or versions of sdm_schemas itself, and not all schemas may be using internal versions.)
 This version may need to be updated when making changes.
 
 Usage of semantic versioning is recommended, which defines a version like `MAJOR.MINOR.PATCH`, such as `1.2.3`.