Improve server install from sources docs

[gdiazlo]

While working on https://github.com/wazuh/wazuh/issues/14323 we have detected improvements to our documentation.

• When installing dependencies, if you copy & paste the whole block of commands it won't work appropriately, as the first command does not have a -y option. This makes the command ask for user input, so it does not execute the other pasted commands.

• Trying to compile Python from source, following the optional instructions does not work, as the package python34 does not exist in Centos 8 latest version. Following the documentation, I've changed to python3 as the package name. Does our code require a specific version of python to work?

  The documentation also says: Nevertheless, you can download the CPython sources by adding the PYTHON_SOURCE flag when running make deps.

  But I was unable to find when to execute that command to add the PYTHON_SOURCE flag.

  Seems this flag is internally used by our install.sh script. This section should probably be deprecated and removed from our documentation.

[Rebits]

Some more suggestions for this documentation page:

• For APT We should replace python dependency with python3
• As specified by @gdiazlo, the optional download of python sources should be included after the Download and extract the latest version step. Also, It could be helpful include the full command required to download the python sources make deps PYTHON_SOURCE=yes