Tutorial 12 constant pH fails with pint 10.1

[espresso-ci]

https://gitlab.icp.uni-stuttgart.de/espressomd/espresso/pipelines/10746

[jngrad]

The constant pH tutorial failed due to the new pint version deployed today in the docker images:
https://gitlab.icp.uni-stuttgart.de/espressomd/espresso/-/jobs/197409

The version went from 0.9 to 10.1. Looking through the release notes, this is probably caused by:

• BREAKING CHANGE:
  Implement NEP-18 https://numpy.org/neps/nep-0018-array-function-protocol.html for
  Pint Quantities. Most NumPy functions that previously stripped units when applied to
  Pint Quantities will now return Quantities with proper units (on NumPy v1.16 with
  the array_function protocol enabled or v1.17+ by default) instead of ndarrays. Any
  non-explictly-handled functions will now raise a "no implementation found" TypeError
  instead of stripping units. The previous behavior is maintained for NumPy < v1.16 and
  when the array_function protocol is disabled.

Also noteworthy:

• BREAKING CHANGE:
  Drop support for Python < 3.6, numpy < 1.14, and uncertainties < 3.0;
  if you still need them, please install pint 0.9.
  Pint now adheres to NEP-29 https://numpy.org/neps/nep-0029-deprecation_policy.html
  as a rolling dependencies version policy.

We could rollback to pint 0.9 until the tutorial gets fixed to avoid a CI deadlock.