[docs/frontend] Update Theme customization documentation (#14115)

[Archidoit]

Proposed changes

Fix documentation about theme screenshots order
Remove useless props enableAskAi
Fix a translation

Related issues

#14115

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 32.36%. Comparing base (c6c09ac) to head (2df690f).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #14667   +/-   ##
=======================================
  Coverage   32.36%   32.36%           
=======================================
  Files        3097     3097           
  Lines      210990   210990           
  Branches    38237    38238    +1     
=======================================
  Hits        68283    68283           
  Misses     142707   142707           

Flag	Coverage Δ
opencti-client-python	45.50% <ø> (ø)
opencti-front	2.83% <ø> (ø)
opencti-graphql	67.73% <ø> (ø)

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