Loading of `*.pcd` point clouds ignores decimals after initializing PyQt's QApplication

### Checklist

- [X] I have searched for [similar issues](https://github.com/isl-org/Open3D/issues).
- [X] For Python issues, I have tested with the [latest development wheel](http://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](http://www.open3d.org/docs/release/) and the [latest documentation](http://www.open3d.org/docs/latest/) (for `master` branch).

### Describe the issue

I am trying to load a `*.pcd` point cloud that contains float positions within a PyQt application. When loading the point cloud using `o3d.io.read_point_cloud()` the points are rounded integers and Open3D ignored the decimal places, which do exist inside the file.

I tracked the bug to only happen after initializing the PyQt application with `QApplication(sys.argv)`. Trying to load the point cloud outside the PyQt application (e.g. in ipython) works fine.

So I assume there must be an interdependence between Open3D and PyQt.

I reproduced this bug with a point cloud provided by sb. issuing this problem for my point cloud labeling tool here: https://github.com/ch-sa/labelCloud/issues/68.
The point cloud was provided here: https://github.com/ch-sa/labelCloud/files/8345198/pointcloud_116.zip.

PyQt-Versions:
```bash
$ conda list | grep qt
pyqt5 5.15.4 pypi_0 pypi
pyqt5-qt5 5.15.2 pypi_0 pypi
pyqt5-sip 12.9.0 pypi_0 pypi
pytest-qt 4.0.2 pypi_0 pypi
```

### Steps to reproduce the bug

```python
import sys

from PyQt5.QtWidgets import QApplication

import open3d as o3d

QApplication(sys.argv)

pcd = o3d.io.read_point_cloud("pointcloud_116.pcd")
print(f"First point: {pcd.points[0]}")
```

### Error message

First point: [-0. 11. 0.]

### Expected behavior

A loaded point cloud with floats:
```bash
First point: [-0.20108423 11.055668 0.56653374]
```
This is the case when I comment `QApplication(sys.argv)` out.

### Open3D, Python and System information

```markdown
- Operating system: Distro: Linux Mint 20.3 Una base: Ubuntu 20.04 focal
- Python version: 3.8.11 (default, Aug 3 2021, 15:09:35) [GCC 7.5.0]
- Open3D version: 0.15.2
- System architecture: x86
- Is this a remote workstation?: no
- How did you install Open3D?: pip (inside conda)

More details can be found here: https://termbin.com/n0go
```

### Additional information

The issue did not appear so far when loading other point cloud formats.