Update README.md to fix a spelling mistake (#33097)

diff --git a/scripts/py_matter_idl/matter_idl/README.md b/scripts/py_matter_idl/matter_idl/README.md
index bd4d3ef..602e856 100644
--- a/scripts/py_matter_idl/matter_idl/README.md
+++ b/scripts/py_matter_idl/matter_idl/README.md
@@ -182,7 +182,7 @@
     content
 -   [matter_idl_parser.py](./matter_idl_parser.py) has a transformer that
     converts the text given by lark into a more type-safe (and type-rich) AST as
-    defined ing [matter_idl_types.py](./matter_idl_types.py)
+    defined in [matter_idl_types.py](./matter_idl_types.py)
 
 ## Code generation