utf8 with BOM fails, lol

Signed-off-by: Basil Bruhn <basil.bruhn@psi.ch>

.github/workflows/release.yml

@@ -146,7 +146,6 @@ jobs:
           } else {
               Write-Host "Environment unchanged → using cached env"
           }
-
       - name: Determine release tag
         shell: powershell
         run: |
@@ -155,7 +154,7 @@ jobs:
 
           Write-Host "Release tag: $tag"
 
-          "RELEASE_TAG=$tag" | Out-File -FilePath $env:GITHUB_ENV -Encoding utf8 -Append
+          Add-Content -Path $env:GITHUB_ENV -Value "RELEASE_TAG=$tag"
 
       - name: Build with pyinstaller
         shell: powershell