Update doc/usage.rst

Co-authored-by: Christine Rose <[email protected]>

doc/usage.rst

@@ -107,7 +107,7 @@ If no ``dune-workspace`` file is present, the same strategy applies with
 In case of a mix of `dune-workspace` and `dune-project` files, workspace files
 take precedence over project files in the sense that if a ``dune-workspace``
 file is found, only parent ``dune-workspace`` files will be considered when
-looking for the root, while if a `dune-project` file is found both parent
+looking for the root; however, if a `dune-project` file is found both parent
 ``dune-workspace`` and ``dune-project`` files will be considered.
 
 A ``dune-workspace`` file is also a configuration file. Dune will read