Enable Poetry's modern installer

[sethfischer]

In 733ab44 Poetry's modern installer was disabled. This was to avoid the following error during a poetry install:

• Installing cadquery-ocp (7.7.0a0): Failed
                                                                                                                                                                                               
  AssertionError
                                                                                               
  In /home/user/.cache/pypoetry/artifacts/d4/3a/a2/5bab70f270aecbf24be39a87376515eafcb88f717fca7180d804b6543b/cadquery_ocp-7.7.0a0-cp39-cp39-manylinux_2_31_x86_64.whl, LICENSES_bundled.txt is
 not mentioned in RECORD
                                                                                               
  at ~/.local/share/pypoetry/venv/lib/python3.8/site-packages/installer/sources.py:158 in get_contents
      154│             if item.filename[-1:] == "/":  # looks like a directory
      155│                 continue
      156│
      157│             record = record_mapping.pop(item.filename, None)
    → 158│             assert record is not None, "In {}, {} is not mentioned in RECORD".format(
      159│                 self._zipfile.filename,
      160│                 item.filename,
      161│             )  # should not happen for valid wheels
      162│

Once cadquery-ocp has been fixed the modern installer should be enabled.

Modern installation was introduced with Poetry 1.4.0.

[sethfischer]

See CadQuery/ocp-build-system#12