[Enhancement]Update checkpoint for model in deeplabv3plus

[MeowZheng]

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Motivation

1. As the model training is sensitive to random seed, we explicitly add random seed for the model.

Modification

1. Results, ckpt URL and log URL of deeplabv3plus_r101-d8_769x769_80k_cityscapes in configs/deeplabv3plus/README.md
2. Results, ckpt URL and log URL of deeplabv3plus_r101-d8_769x769_80k_cityscapes in
3. configs/deeplabv3plus/deeplabv3plus.yml

BC-breaking (Optional)

Does the modification introduce changes that break the backward-compatibility of the downstream repos?
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 test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects, like MMDet or MMDet3D.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[codecov]

Codecov Report

Merging #1487 (4f148be) into master (5b605b0) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1487   +/-   ##
=======================================
  Coverage   90.30%   90.30%           
=======================================
  Files         140      140           
  Lines        8335     8338    +3     
  Branches     1400     1402    +2     
=======================================
+ Hits         7527     7530    +3     
  Misses        570      570           
  Partials      238      238           

Flag	Coverage Δ
unittests	90.30% <ø> (+<0.01%)	⬆️

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Impacted Files	Coverage Δ
mmseg/models/losses/accuracy.py	100.00% <0.00%> (ø)

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