ci: bump actions/checkout from v3 to v4

* pytorch.yml
* tflite.yml

Signed-off-by: Yi Huang <yi@secondstate.io>

Author: 0yi0

.github/workflows/pytorch.yml

@@ -28,7 +28,7 @@ jobs:
       image: ubuntu:20.04
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: Install apt-get packages
       run: |

.github/workflows/tflite.yml

@@ -28,7 +28,7 @@ jobs:
       image: ubuntu:20.04
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: Install apt-get packages
       run: |