docs: fix code examples for setting-up-ide and interpreter-compatibility docs (Cherry-pick of #19624)

[WorkerPants]

Setting Up IDE Doc Issue

Currently, in the docs/markdown/Using Pants/setting-up-an-ide.md page, the project instructs users to run

$ ROOTS=$(pants roots --roots-sep=' ')
$ python3 -c "print('PYTHONPATH=\"./' + ':./'.join(\"${ROOTS}\".split()) + ':\$PYTHONPATH\"')" > .env

However, for some reason, the command pants roots --roots-sep=' ' is not working for the ' ' character. This PR makes a small fix to this issue changing the ' ' character to the default '\n' by removing the --roots-sep= argument and changing how the ROOTS environment variable is split.

$ ROOTS=$(pants roots)
$ python3 -c "print('PYTHONPATH=\"./' + ':./'.join('''${ROOTS}'''.split('\n')) + ':\$PYTHONPATH\"')" > .env

Alternatively, if we want to maintain the roots-sep argument, so users know it exists, we can change it from ' ' to a non whitespace character, such as ';' and that also seems to work.

Interpreter Compatibility Doc Issue

Another small issue is in docs/markdown/Python/python/python-interpreter-compatibility.md in the example:

python_sources(
    name="lib",
    overrides={
        "py2.py": {"interpreter_constraints": ["==2.7.*"]},
        # You can use a tuple for multiple files:
        ("common.py", "f.py"): {"interpreter_constraints": ["==2.7.*"]},
)

This example is missing an }. This PR also addresses this small issue.