[Fix] fix 1d heatmap visualization problem

[nixsui]

Fix 1d heatmap visualization problem, change the method of generating background image from：

        blank = np.zeros((size[0] * 2, size[1] * 2, 3), np.uint8)

to:

        blank_height = int(
            max(size[0] * 2, size[0] * 1.1 + (K + 1) * (15 + interval)))
        blank_width = int(
            max(size[1] * 2, size[1] * 1.1 + (K + 1) * (15 + interval)))
        blank = np.zeros((blank_height, blank_width, 3), np.uint8)

[CLAassistant]

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[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.01 🎉

Comparison is base (3af7fed) 81.46% compared to head (c0d1d4c) 81.47%.

❗ Current head c0d1d4c differs from pull request most recent head 0e70aff. Consider uploading reports for the commit 0e70aff to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           dev-1.x    #2092      +/-   ##
===========================================
+ Coverage    81.46%   81.47%   +0.01%     
===========================================
  Files          227      227              
  Lines        13513    13515       +2     
  Branches      2306     2306              
===========================================
+ Hits         11008    11012       +4     
+ Misses        1987     1983       -4     
- Partials       518      520       +2     

Flag	Coverage Δ
unittests	81.47% <100.00%> (+0.01%)	⬆️

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

Impacted Files	Coverage Δ
mmpose/visualization/simcc_vis.py	98.66% <100.00%> (+0.03%)	⬆️

... and 1 file with indirect coverage changes

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[OpenMMLab-Assistant-004]

Hi @nixsui ！First of all, we want to express our gratitude for your significant PR in the mmpose project. Your contribution is highly appreciated, and we are grateful for your efforts in helping improve this open-source project during your personal time. We believe that many developers will benefit from your PR.

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