update batch index

[grimoire]

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Motivation

Batched cascade roi head has wrong batch id.
#1945

Modification

Update batch id.

BC-breaking (Optional)

Does the modification introduce changes that break the backward-compatibility of the downstream repositories?
If so, please describe how it breaks the compatibility and how the downstream projects should modify their code to keep compatibility with this PR.

Use cases (Optional)

If this PR introduces a new feature, it is better to list some use cases here, and update the documentation.

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit tests to ensure the correctness.
3. If the modification has a dependency on downstream projects of a newer version, this PR should be tested with all supported versions of downstream projects.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (26b66ef) 49.70% compared to head (ef52ee6) 49.70%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2078   +/-   ##
=======================================
  Coverage   49.70%   49.70%           
=======================================
  Files         339      339           
  Lines       12976    12976           
  Branches     1900     1900           
=======================================
  Hits         6450     6450           
  Misses       6077     6077           
  Partials      449      449           

Flag	Coverage Δ
unittests	49.70% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...odebase/mmdet/models/roi_heads/cascade_roi_head.py	100.00% <100.00%> (ø)

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[RunningLeon]

LGTM