Remove install of packages with pip

[Jannik-Schilling]

[Some kind of disclaimer]: I didn´t try this myself. Someone reported an issue with this plugin on the QGIS telegram group, while trying to install the plugin on a Linux platform.

The line
subprocess.call([get_qgis_python_path(), “-m”, “pip”, “install”, “ptvsd”])
from this part led to an FileNotFoundError. As you can see here, installing depencies with pip has been discussed many times. Therefore, the requirements for publishing a plugin (see https://plugins.qgis.org/publish/), say: "If the plugin has an external dependency, this needs to be clearly stated in the About metadata field; you can include a short guide to install Python libs as needed"

[KatKatKateryna]

Good point! We will need to work this out before removing Experimental flag.

Since the latest release all dependencies are being installed to a custom folder, therefore not affecting user's Python setup, and the reported issue seems to be using the outdated plugin version