ci: fix Windows ARM64 target name

Change Windows ARM64 target from 'arm64' to 'aarch64' to match the
Rust target triple format expected by maturin-action.

The error was: "could not find specification for target 'arm64'"

Author: claude

.github/workflows/publish-pypi.yaml

@@ -73,7 +73,7 @@ jobs:
             python-architecture: x86
           - os: windows
             interpreter: 3.10 3.11 3.12 3.13 3.14 # no pypy
-            target: arm64
+            target: aarch64
 
     runs-on: ${{ (matrix.os == 'linux' && 'ubuntu') || matrix.os }}-latest
     steps: