[Fix] Fix config of ImVoteNet

[yezhen17]

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Motivation

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BC-breaking caused by open-mmlab/mmdetection#5205

Modification

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BC-breaking (Optional)

Does the modification introduce changes that break the back-compatibility of the downstream repos?
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Use cases (Optional)

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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 test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[codecov]

Codecov Report

Merging #828 (0a74216) into master (31ef559) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #828   +/-   ##
=======================================
  Coverage   49.07%   49.07%           
=======================================
  Files         210      210           
  Lines       15961    15961           
  Branches     2547     2547           
=======================================
  Hits         7833     7833           
  Misses       7626     7626           
  Partials      502      502           

Flag	Coverage Δ
unittests	49.07% <ø> (ø)

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