Do not force pre-release versions of resolwe

[acopar]

Prevents installing prereleases when no --pre flag is given to pip install. Pull request changes this behavior:

$ cat requirements-pre.txt 
resolwe>=42.0a1, ==42.*
$ pip install -r requirements-pre.txt
$ pip freeze | grep -i resolwe                                                                                                                                                                        
resolwe==42.1.0a3

to this behavior:

$ cat requirements-stable.txt                                                                                                                                                                                                 
resolwe==42.*
$ pip install -r requirements-stable.txt
$ pip freeze | grep -i resolwe                                                                                                                                                                       
resolwe==42.0.2
$ pip uninstall resolwe

$ pip install --pre -r requirements-stable.txt
$ pip freeze | grep -i resolwe                                                                                                                                                                        
resolwe==42.1.0a3

Tested with Python3.11 and Pip 24.3.1