[Fix] Fix the incorrect labels for training vis_head with combined datasets

[Ben-Louis]

Motivation

Modification

BC-breaking (Optional)

Use cases (Optional)

Checklist

Before PR:

• I have read and followed the workflow indicated in the CONTRIBUTING.md to create this PR.
• Pre-commit or linting tools indicated in CONTRIBUTING.md are used to fix the potential lint issues.
• Bug fixes are covered by unit tests, the case that causes the bug should be added in the unit tests.
• New functionalities are covered by complete unit tests. If not, please add more unit tests to ensure correctness.
• The documentation has been modified accordingly, including docstring or example tutorials.

After PR:

• CLA has been signed and all committers have signed the CLA in this PR.

[codecov]

Codecov Report

Patch coverage: 68.75% and project coverage change: -0.05% ⚠️

Comparison is base (5e862cc) 80.83% compared to head (85d16ea) 80.79%.
Report is 19 commits behind head on dev-1.x.

❗ Current head 85d16ea differs from pull request most recent head 6145d3f. Consider uploading reports for the commit 6145d3f to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           dev-1.x    #2550      +/-   ##
===========================================
- Coverage    80.83%   80.79%   -0.05%     
===========================================
  Files          230      230              
  Lines        14403    14469      +66     
  Branches      2489     2507      +18     
===========================================
+ Hits         11643    11690      +47     
- Misses        2122     2131       +9     
- Partials       638      648      +10     

Flag	Coverage Δ
unittests	80.79% <68.75%> (-0.05%)	⬇️

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

Files Changed	Coverage Δ
mmpose/datasets/transforms/common_transforms.py	84.25% <0.00%> (-0.28%)	⬇️
mmpose/datasets/transforms/formatting.py	79.76% <ø> (+1.85%)	⬆️
...s/heads/regression_heads/motion_regression_head.py	28.78% <11.11%> (-2.25%)	⬇️
mmpose/codecs/motionbert_label.py	75.55% <28.57%> (-2.86%)	⬇️
mmpose/models/pose_estimators/pose_lifter.py	37.28% <37.50%> (-0.55%)	⬇️
mmpose/models/pose_estimators/bottomup.py	70.00% <50.00%> (-0.69%)	⬇️
mmpose/models/pose_estimators/topdown.py	67.79% <50.00%> (-0.63%)	⬇️
mmpose/visualization/local_visualizer.py	63.40% <60.00%> (+1.09%)	⬆️
mmpose/apis/inferencers/pose3d_inferencer.py	82.72% <66.66%> (+0.09%)	⬆️
mmpose/models/heads/hybrid_heads/vis_head.py	83.15% <70.83%> (-4.94%)	⬇️
... and 9 more

... and 2 files with indirect coverage changes

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[Tau-J]

Have you checked the influence on browse_dataset.py ?

[Ben-Louis]

Have you checked the influence on browse_dataset.py ?

Yes, I tried to browse the combined dataset body7, and the results seem reasonable