fix punctuation

Author: vladimir-dudnik

demos/interactive_face_detection_demo/cpp/README.md

@@ -94,7 +94,7 @@ Options:
 
 Running the application with an empty list of options yields the usage message given above and an error message.
 
-To run the demo, you can use public or Intel pre-trained models. You can download models and if necessary convert them into Inference Engine format using the [Model Downloader and other automation tools](../../../tools/downloader/README.md) as shown in the examples below. The models which are supported by the demo are listed in the [models.lst](./models.lst) file.
+To run the demo, you can use public or Intel pre-trained models. You can download models and, if necessary, convert them into Inference Engine format using the [Model Downloader and other automation tools](../../../tools/downloader/README.md) as shown in the examples below. The models which are supported by the demo are listed in the [models.lst](./models.lst) file.
 
 An example of using the Model Downloader:
 ```

demos/interactive_face_detection_demo/cpp_gapi/README.md

@@ -67,7 +67,7 @@ Options:
 
 Running the application with an empty list of options yields the usage message given above and an error message.
 
-To run the demo, you can use public or Intel pre-trained models. You can download models and if necessary convert them into Inference Engine format using the [Model Downloader and other automation tools](../../../tools/downloader/README.md) as shown in the examples below. The models which are supported by the demo are listed in the [models.lst](./models.lst) file.
+To run the demo, you can use public or Intel pre-trained models. You can download models and, if necessary, convert them into Inference Engine format using the [Model Downloader and other automation tools](../../../tools/downloader/README.md) as shown in the examples below. The models which are supported by the demo are listed in the [models.lst](./models.lst) file.
 
 An example of using the Model Downloader:
 ```