[AGIPD] [CORRECT] `keep_dims` if only one cellId is corrected

This fixes the issue from this ticket https://redmine.xfel.eu/issues/143284

Description

This was an old MR to solve correcting 1 cellId for AGIPD: /gpfs/exfel/exp/MID/202230/p900249/usr/Reports/r198/MID_DET_AGIPD1M-1_correct_900249_r198_220308_223408.pdf

1. EXtra_data creates arrays without the cell dimension. Use keep_dims
2. Remove temporary workaround.
3. This fixes a bug faced when use_litframe_finder is on. As the cell_sel is switched from the expected CellRange to LitFrameSelection: /gpfs/exfel/exp/MID/202231/p900310/usr/Reports/r400/MID_DET_AGIPD1M-1_correct_900310_r400_221111_011350.pdf

How Has This Been Tested?

Reference runs and processing run 198 with 1 cellId as

Relevant Documents (optional)

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

Reviewers

@schmidtp @roscar @kluyvert