Fix nits in LOCAL_VIRTUALENV.rst

[EricGao888]

• In "https://raw.githubusercontent.com/apache/airflow/constraints-main/constraints-3.8.txt" we get docutils==0.20.1, which conflicts with

  airflow/setup.py

  Line 303 in 4a9824d

  "docutils<0.17.0",

  . After changing it to "https://raw.githubusercontent.com/apache/airflow/constraints-main/constraints-source-providers-3.8.txt", things work well.
• BTW, I think

  airflow/LOCAL_VIRTUALENV.rst

  Line 254 in 4a9824d

  INSTALL_PROVIDERS_FROM_SOURCES="true" pip install -U -e ".[devel,<OTHER EXTRAS>]" \

-e flag works negatively here. I had spent quite some time with the environment errors when using this install command. After I had removed the -e flag, things started to work.

With -e flag, I got some errors like:

ERROR:airflow.configuration:cannot import name '__version__' from 'airflow' (unknown location)
ERROR:airflow.cli.cli_parser:cannot load CLI commands from auth manager

If -e no more works here, what about removing it? In case the instruction causes trouble for other developers.

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[potiuk]

Re -e, yes we have an issu about that #30764 and I am about to turn my attention to get it fixed.