Contributing.md: fix typo
@@ -198,7 +198,7 @@ The (optional) `test.json` file, in the root of a test case, is used
for configuring the test. All of the following root entries in the `test.json`
are independent of each other and can be combined as needed.
-Exanple `test.json`:
+Example `test.json`:
```json
{
