Fix compile error due to GetModuleFileNameW binding change

In #19641, this binding changed from `[*]u16` to `LPWSTR` which made it a sentinel-terminated pointer. This introduced a compiler error in the `std.os.windows.GetModuleFileNameW` wrapper since it takes a `[*]u16` pointer. This commit changes the binding back to what it was before instead of introducing a breaking change to `std.os.windows.GetModuleFileNameW`

Related: #20858

Author: squeek502

lib/std/os/windows/kernel32.zig

@@ -597,7 +597,7 @@ pub extern "kernel32" fn GetProcessHeap() callconv(WINAPI) ?HANDLE;
 // TODO: Wrapper around LdrGetDllFullName.
 pub extern "kernel32" fn GetModuleFileNameW(
     hModule: ?HMODULE,
-    lpFilename: LPWSTR,
+    lpFilename: [*]WCHAR,
     nSize: DWORD,
 ) callconv(WINAPI) DWORD;