Upgrade Kotlin to MacOS 15 (google#8845)

* upgrade kotlin and macos

* remove xcode version selection

Author: jtdavis777

.github/workflows/build.yml

@@ -390,17 +390,10 @@ jobs:
 
   build-kotlin-macos:
     name: Build Kotlin MacOS
-    runs-on: macos-13
+    runs-on: macos-15
     steps:
     - name: Checkout
       uses: actions/checkout@v6
-      # Force Xcode 14.3 since Xcode 15 doesnt support older versions of
-      # kotlin. For Xcode 15, kotlin should be bumpped to 1.9.10
-      # https://stackoverflow.com/a/77150623
-      # For now, run with macos-13 which has this 14.3 installed:
-      # https://github.com/actions/runner-images/blob/main/images/macos/macos-13-Readme.md#xcode
-    - name: Set up Xcode version
-      run: sudo xcode-select -s /Applications/Xcode_14.3.app/Contents/Developer
     - name: set up Java
       uses: actions/setup-java@v4
       with:

kotlin/gradle/libs.versions.toml

@@ -2,7 +2,7 @@
 # Version 1.9.10 fix
 # https://youtrack.jetbrains.com/issue/KT-60230/Native-unknown-options-iossimulatorversionmin-sdkversion-with-Xcode-15-beta-3
 kotlin = "1.9.10"
-plugin-kotlin = "1.6.10"
+plugin-kotlin = "1.9.10"
 plugin-gver = "0.42.0"
 kotlinx-benchmark = "0.4.8"
 junit = "4.12"