Update README for v2

Update the README examples for v2.

README.md

@@ -10,8 +10,8 @@ An example Pull Request created by the action can be found [here](https://github
 
 ```yml
 steps:
-- uses: actions/checkout@v2
-- uses: martincostello/update-dotnet-sdk@v1
+- uses: actions/checkout@v3
+- uses: martincostello/update-dotnet-sdk@v2
   with:
     repo-token: ${{ secrets.GITHUB_TOKEN }}
 ```
@@ -37,8 +37,8 @@ jobs:
     name: Update .NET SDK
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
-    - uses: martincostello/update-dotnet-sdk@v1
+    - uses: actions/checkout@v3
+    - uses: martincostello/update-dotnet-sdk@v2
       with:
         repo-token: ${{ secrets.GITHUB_TOKEN }}
 ```
@@ -56,7 +56,7 @@ jobs:
 | **Name** | **Description** | **Default** |
 |:--|:--|:--|
 | `branch-name` | The optional Git branch name to use. | - |
-| `channel` | The optional .NET release channel to download the SDK for (2.1, 3.1, 5.0, etc.). | The channel derived from the current SDK version. |
+| `channel` | The optional .NET release channel to download the SDK for (3.1, 6.0, etc.). | The channel derived from the current SDK version. |
 | `commit-message` | The optional Git commit message to use. | - |
 | `global-json-file` | The optional path to the global.json file to update the SDK for. | `./global.json` |
 | `labels` | The optional comma-separated label(s) to apply to Pull Requests generated by the action. | - |