[AIRFLOW-XXXX] Remove "Core and community package" section

[mik-laj]

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Issue link: Document only change, no JIRA issue

Make sure to mark the boxes below before creating PR: [x]

• Description above provides context of the change
• Commit message/PR title starts with [AIRFLOW-NNNN]. AIRFLOW-NNNN = JIRA ID^*
• Unit tests coverage for changes (not needed for documentation changes)
• Commits follow "How to write a good git commit message"
• Relevant documentation is updated including usage instructions.
• I will engage committers as explained in Contribution Workflow Example.

^* For document-only changes commit message can start with [AIRFLOW-XXXX].

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In case of fundamental code change, Airflow Improvement Proposal (AIP) is needed.
In case of a new dependency, check compliance with the ASF 3rd Party License Policy.
In case of backwards incompatible changes please leave a note in UPDATING.md.
Read the Pull Request Guidelines for more information.

[codecov-io]

Codecov Report

Merging #7361 into master will increase coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #7361      +/-   ##
==========================================
+ Coverage   86.35%   86.35%   +<.01%     
==========================================
  Files         871      871              
  Lines       40627    40627              
==========================================
+ Hits        35082    35083       +1     
+ Misses       5545     5544       -1

Impacted Files	Coverage Δ
airflow/utils/dag_processing.py	88.12% <0%> (+0.19%)	⬆️

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