[CI][C++] Meson build is broken: File fixed_shape_tensor_test.cc does not exist

### Describe the bug, including details regarding any error messages, version, and platform.

https://github.com/apache/arrow/actions/runs/22696281103/job/65803283099#step:6:531

```text
../../arrow/cpp/src/arrow/extension/meson.build:27:6: ERROR: File fixed_shape_tensor_test.cc does not exist.
```

#38008 may be related.

### Component(s)

C++, Continuous Integration