[BUG] CLI forecast command fails with pipeline ensembles

[brsnw250]

Before submitting (must do checklist)

• Did you read the contribution guide?
• Did you update the docs? We use Numpy format for all the methods and classes.
• Did you write any new necessary tests?
• Did you update the CHANGELOG?

Proposed Changes

Closing issues

closes #1329

[codecov-commenter]

Codecov Report

Merging #1331 (036fa07) into master (cd93027) will increase coverage by 0.01%.
The diff coverage is 100.00%.

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@@            Coverage Diff             @@
##           master    #1331      +/-   ##
==========================================
+ Coverage   89.09%   89.11%   +0.01%     
==========================================
  Files         204      204              
  Lines       12638    12641       +3     
==========================================
+ Hits        11260    11265       +5     
+ Misses       1378     1376       -2     

Files Changed	Coverage Δ
etna/commands/forecast_command.py	95.00% <100.00%> (+0.19%)	⬆️

... and 1 file with indirect coverage changes

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[github-actions]

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