Update used GitHub Actions

Author: rosenbjerg

.github/workflows/ci.yml

@@ -18,12 +18,12 @@ jobs:
     timeout-minutes: 6
     steps:
     - name: Checkout
-      uses: actions/checkout@v1
+      uses: actions/checkout@v2
     - name: Prepare .NET
       uses: actions/setup-dotnet@v1
       with:
         dotnet-version: '5.0.x'
     - name: Prepare FFMpeg
-      uses: FedericoCarboni/setup-ffmpeg@v1-beta
+      uses: FedericoCarboni/setup-ffmpeg@v1
     - name: Test with dotnet
       run: dotnet test --logger GitHubActions

.github/workflows/release.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Checkout
-      uses: actions/checkout@v1
+      uses: actions/checkout@v2
     - name: Prepare .NET
       uses: actions/setup-dotnet@v1
       with: