Drop unnecessary forced net6 install

It's built-in agents already

Author: kzu

.github/workflows/build.yml

@@ -53,12 +53,6 @@ jobs:
           submodules: recursive
           fetch-depth: 0
 
-      - name: ⚙ dotnet
-        uses: actions/setup-dotnet@v1
-        if: matrix.os != 'windows-latest'
-        with:
-          dotnet-version: '6.0.x'
-
       - name: 🙏 build
         run: dotnet build -m:1 -p:VersionLabel="$GITHUB_REF.$GITHUB_RUN_NUMBER"
 
@@ -93,10 +87,5 @@ jobs:
           submodules: recursive
           fetch-depth: 0
 
-      - name: ⚙ dotnet
-        uses: actions/setup-dotnet@v1
-        with:
-          dotnet-version: '6.0.x'
-
       - name: ✓ ensure format
         run: dotnet format --verify-no-changes -v:diag --exclude ~/.nuget

.github/workflows/publish.yml

@@ -21,11 +21,6 @@ jobs:
           submodules: recursive
           fetch-depth: 0
 
-      - name: ⚙ dotnet
-        uses: actions/setup-dotnet@v1
-        with:
-          dotnet-version: '6.0.x'
-
       - name: 🙏 build
         run: dotnet build -m:1 -p:version=${GITHUB_REF#refs/*/v}