CI: restore PyPI installation

[gcroci2]

In this PR:

• I removed all the pip installable packages from the deeprank.yml and I moved them back into the pyproject.toml file. This way they will be package together with the package on pip, and pip install deeprank2 will take care of installing them all.
• I found a way for installing pip packages within the env defined in the dockerfile. After this PR will be merged, I will do a new pip release (which will contain the pip dependencies) and I'll delete the deeprank2-docker.yml and requirements-docker.txt files, since they are not needed anymore (I will pip install deeprank2 together with its pip dependencies in the dockerfile).
• No need to update the instructions for the installation.

[coveralls]

coverage: 83.933%. remained the same
when pulling c0c77f3 on remove_conda_deps
into 73969e6 on main.

[coveralls]

coverage: 83.818% (-0.1%) from 83.933%
when pulling ee08b3a on remove_conda_deps
into 73969e6 on main.

[coveralls]

coverage: 83.933%. remained the same
when pulling 28afabe on remove_conda_deps
into 73969e6 on main.

[coveralls]

coverage: 83.933%. remained the same
when pulling 8403245 on remove_conda_deps
into 73969e6 on main.

[coveralls]

coverage: 83.818% (-0.1%) from 83.933%
when pulling 56929ff on remove_conda_deps
into 73969e6 on main.

[coveralls]

coverage: 83.933%. remained the same
when pulling 289719a on remove_conda_deps
into 73969e6 on main.

[coveralls]

coverage: 83.933%. remained the same
when pulling 90a6c06 on remove_conda_deps
into 73969e6 on main.

[coveralls]

coverage: 83.818% (-0.1%) from 83.933%
when pulling 0ca24d2 on remove_conda_deps
into 73969e6 on main.