Update checkout action to latest version (#5021)

Latest checkout uses latest (non-deprecated) version of node (16 -> 20).

More information
[here](https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/):
```
Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: actions/checkout@v3. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.
```

Checkout action: https://github.com/actions/checkout

Node 20 requires a minimum of Ubuntu 20.04, so workflows currently using
18.04 are failing/will fail.

.github/workflows/cpu-inference.yml

@@ -27,7 +27,7 @@ jobs:
     env: {ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION: true} # Allow using Node16 actions
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - id: setup-venv
         uses: ./.github/workflows/setup-venv

.github/workflows/nv-lightning-v100.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: [self-hosted, nvidia, cu121, v100]
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - id: setup-venv
         uses: ./.github/workflows/setup-venv

.github/workflows/nv-torch110-p40.yml

@@ -20,7 +20,7 @@ jobs:
     env: {ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION: true} # Allow using Node16 actions
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - id: setup-venv
         uses: ./.github/workflows/setup-venv

.github/workflows/nv-torch110-v100.yml

@@ -20,7 +20,7 @@ jobs:
     env: {ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION: true} # Allow using Node16 actions
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - id: setup-venv
         uses: ./.github/workflows/setup-venv