[nrfconnect] Repaired wrong script invocation for factory data

The factory data documentation contains the wrong example of
the factory data script invocation and it did not allow users to use it.

docs/guides/nrfconnect_factory_data_configuration.md

@@ -247,7 +247,7 @@ To use this script, complete the following steps:
     b. Add output file path:
 
     ```
-    -o <output_dir>
+    -o <path_to_output_json_file>
     ```
 
     c. Generate SPAKE2 verifier using one of the following methods:
@@ -357,7 +357,7 @@ $ python scripts/tools/nrfconnect/generate_nrfconnect_chip_factory_data.py \
 --passcode 20202021 \
 --product_finish "matte" \
 --product_color "black" \
---out "build.json"' \
+--out "build.json" \
 --schema "scripts/tools/nrfconnect/nrfconnect_factory_data.schema"
 ```