GHA: Drop beta, use Xcode 26.0.0

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Author: helje5

.github/workflows/swift.yml

@@ -38,10 +38,10 @@ jobs:
   xcode26:
     runs-on: macos-15
     steps:
-      - name: Select Xcode 26-beta
+      - name: Select Xcode 26
         uses: maxim-lobanov/setup-xcode@v1.6.0
         with:
-          xcode-version: 26-beta
+          xcode-version: 26.0.0
       - name: Checkout Repository
         uses: actions/checkout@v4
       - name: Build Swift Debug Package