updated README and Podfile to PT 1.9 for ObjectDetection

Author: jeffxtang

ObjectDetection/Podfile

@@ -6,5 +6,5 @@ target 'ObjectDetection' do
   use_frameworks!
 
   # Pods for ObjectDetection
-  pod 'LibTorch', '~>1.7.0'
+  pod 'LibTorch', '~>1.9.0'
 end

ObjectDetection/README.md

@@ -6,9 +6,9 @@
 
 ## Prerequisites
 
-* PyTorch 1.7 or later (Optional)
+* PyTorch 1.9.0 or later (Optional)
 * Python 3.8 (Optional)
-* iOS Pytorch pod library 1.7
+* iOS Cocoapods library LibTorch 1.9.0
 * Xcode 12 or later
 
 ## Quick Start
@@ -19,7 +19,7 @@ To Test Run the Object Detection iOS App, follow the steps below:
 
 If you don't have the PyTorch environment set up to run the script, you can download the model file [here](https://drive.google.com/file/d/1QOxNfpy_j_1KbuhN8INw2AgAC82nEw0F/view?usp=sharing) to the `ios-demo-app/ObjectDetection/ObjectDetection` folder, then skip the rest of this step and go to step 2 directly.
 
-Be aware that the downloadable model file was created with PyTorch 1.7.0, matching the iOS LibTorch library 1.7.0 specified in the `Podfile`. If you use a different version of PyTorch to create your model by following the instructions below, make sure you specify the same iOS LibTorch version in the `Podfile` to avoid possible errors caused by the version mismatch. Furthermore, if you want to use the latest prototype features in the PyTorch master branch to create the model, follow the steps at [Building PyTorch iOS Libraries from Source](https://pytorch.org/mobile/ios/#build-pytorch-ios-libraries-from-source) on how to use the model in iOS.
+Be aware that the downloadable model file was created with PyTorch 1.9.0, matching the iOS LibTorch library 1.9.0 specified in the `Podfile`. If you use a different version of PyTorch to create your model by following the instructions below, make sure you specify the same iOS LibTorch version in the `Podfile` to avoid possible errors caused by the version mismatch. Furthermore, if you want to use the latest prototype features in the PyTorch master branch to create the model, follow the steps at [Building PyTorch iOS Libraries from Source](https://pytorch.org/mobile/ios/#build-pytorch-ios-libraries-from-source) on how to use the model in iOS.
 
 The Python script `export.py` in the `models` folder of the [YOLOv5 repo](https://github.com/ultralytics/yolov5) is used to generate a TorchScript-formatted YOLOv5 model named `yolov5s.torchscript.pt` for mobile apps.