[AIRFLOW-6837] limit description len of dag in home

[pingzh]

as it makes dags link not clickable

The dag with long description:

Before:

After:

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Issue link: AIRFLOW-6837

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].

---

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 #7457 into master will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #7457      +/-   ##
==========================================
+ Coverage   86.74%   86.78%   +0.04%     
==========================================
  Files         883      886       +3     
  Lines       41635    41975     +340     
==========================================
+ Hits        36116    36428     +312     
- Misses       5519     5547      +28

Impacted Files	Coverage Δ
airflow/utils/dag_processing.py	87.93% <0%> (-0.2%)	⬇️
airflow/providers/google/cloud/hooks/datafusion.py	81.3% <0%> (ø)
...rs/google/cloud/example_dags/example_datafusion.py	93.1% <0%> (ø)
...low/providers/google/cloud/operators/datafusion.py	97.54% <0%> (ø)

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[kaxil]

Can you rebase to latest master and resolve the conflicts

[pingzh]

Can you rebase to latest master and resolve the conflicts

Rebased. thanks