[Bug]: target argument are still required by install-src

[trim21]

Bug description

/opt/hostedtoolcache/Python/3.11.9/x64/bin/python3 -m aqt install-src linux 6.5.* --outputdir /home/runner/work/actions-cron/Qt --archives qtbase fall to run becase aqt think target is "None"

but document says it's deprecated and its value is ignored.

ERROR   : Target 'None' is invalid
Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.11.9/x64/lib/python3.11/site-packages/aqt/installer.py", line 108, in run
    args.func(args)
  File "/opt/hostedtoolcache/Python/3.11.9/x64/lib/python3.11/site-packages/aqt/installer.py", line 423, in run_install_src
    Cli._determine_qt_version(args.qt_version_spec, args.host, args.target, arch="", base_url=base)
  File "/opt/hostedtoolcache/Python/3.11.9/x64/lib/python3.11/site-packages/aqt/installer.py", line 225, in _determine_qt_version
    version = choose_highest(version, opt_version_for_spec(ext, spec))
                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/hostedtoolcache/Python/3.11.9/x64/lib/python3.11/site-packages/aqt/installer.py", line 210, in opt_version_for_spec
    return MetadataFactory(ArchiveId("qt", host, target, ext), spec=_spec, base_url=base_url).getList().latest()
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/hostedtoolcache/Python/3.11.9/x64/lib/python3.11/site-packages/aqt/metadata.py", line 226, in __init__
    raise ValueError("Target '{}' is invalid".format(target))
ValueError: Target 'None' is invalid
ERROR   : aqtinstall(aqt) v3.0.4 on Python 3.11.9 [CPython GCC 13.2.0]
Working dir: `/home/runner/work/actions-cron/actions-cron`
Arguments: `['/opt/hostedtoolcache/Python/3.11.9/x64/lib/python3.11/site-packages/aqt/__main__.py', 'install-src', 'linux', '6.5.*', '--outputdir', '/home/runner/work/actions-cron/Qt', '--archives', 'qtbase']` Host: `uname_result(system='Linux', node='fv-az1670-614', release='6.8.0-1007-azure', version='#7-Ubuntu SMP Sat Apr 20 00:06:31 UTC 2024', machine='x86_64')`
===========================PLEASE FILE A BUG REPORT===========================
You have discovered a bug in aqt.

Expected behavior

should install source as expected

aqt and python version

aqtinstall(aqt) v3.0.4 on Python 3.11.9 [CPython GCC 13.2.0]

or with version 3.1.*

Operating System

Linux/Unix

Relevant log output

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[pzhlkj6612]

Downstream issue:

• can not install src with source: true jurplel/install-qt-action#243

[trim21]

I'm guessing it's caused by this:

aqtinstall/aqt/installer.py

Line 859 in f049a82

default=None,

default value None is convert to 'None' by argparse, but install-src still use it