Update to macOS 26 in CI

This doesn't update the x86_64 version as macos-26-intel doesn't seem to
exist, so we're sticking with macos-15-intel.

Author: Thomasdezeeuw

.github/workflows/ci.yaml

@@ -39,7 +39,7 @@ jobs:
     name: Clippy on ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-24.04, macos-15, windows-2025]
+        os: [ubuntu-24.04, macos-26, windows-2025]
     runs-on: ${{ matrix.os }}
     timeout-minutes: 10
     steps:
@@ -117,7 +117,7 @@ jobs:
       matrix:
         include:
           - target: aarch64-apple-darwin
-            os: macos-15
+            os: macos-26
           - target: aarch64-pc-windows-msvc
             os: windows-11-arm
           - target: aarch64-unknown-linux-gnu