[AIRFLOW-6353] security - ui - add click jacking defence

[tooptoop4]

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• Commit message contains [AIRFLOW-6353] or [AIRFLOW-XXXX] for document-only changes
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[tooptoop4]

@mik-laj pls merge (continuation of #6911)

[codecov-io]

Codecov Report

Merging #6995 into master will decrease coverage by <.01%.
The diff coverage is 80%.

@@            Coverage Diff             @@
##           master    #6995      +/-   ##
==========================================
- Coverage   84.85%   84.84%   -0.01%     
==========================================
  Files         679      679              
  Lines       38536    38541       +5     
==========================================
+ Hits        32698    32702       +4     
- Misses       5838     5839       +1

Impacted Files	Coverage Δ
airflow/www/app.py	94.02% <80%> (-0.55%)	⬇️

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