os.windows.OpenFile: Add `USER_MAPPED_FILE` as a possible error

Ran into this when using a program that uses CreateFileMapping and then trying to call `std.fs.createFile` on the mapped file. More info can be found here:

https://stackoverflow.com/questions/41844842/when-error-1224-error-user-mapped-file-occurs

Before:

```
error.Unexpected NTSTATUS=0xc0000243
C:\Users\Ryan\Programming\Zig\zig\lib\std\os\windows.zig:138:40: 0x7ff74e957466 in OpenFile (test.exe.obj)
        else => return unexpectedStatus(rc),
                                       ^
```

After:

```
FAIL (AccessDenied)
C:\Users\Ryan\Programming\Zig\zig\lib\std\os\windows.zig:137:30: 0x7ff7f5b776ea in OpenFile (test.exe.obj)
        .USER_MAPPED_FILE => return error.AccessDenied,
                             ^
```

0 files changed, 0 insertions, 0 deletions