Use Xcode 15.4

Author: itaybre

.github/workflows/build-xcframework-variant-slices.yml

@@ -67,12 +67,8 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      # We have to compile on Xcode 15.2 because compiling on Xcode 15.4 fails with
-      # Data+SentryTracing.swift:21:62: error: 'ReadingOptions' aliases 'Foundation.ReadingOptions'
-      # and cannot be used here because C++ types from imported module 'Foundation' do not support
-      # library evolution; this is an error in the Swift 6 language mode
-      # We also can't use Xcode 16.x because validating the XCFramework then fails with Xcode 15.x.
-      - run: ./scripts/ci-select-xcode.sh 15.2
+      # We can't use Xcode 16.x because validating the XCFramework then fails with Xcode 15.x.
+      - run: ./scripts/ci-select-xcode.sh 15.4
         shell: bash
 
       - name: Get version