Modify http to https when installing mmcv-full

[yl-1993]

HTTP will be ignored as it is not a trusted or secure host.

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[codecov]

Codecov Report

Merging #3840 into master will decrease coverage by 0.10%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3840      +/-   ##
==========================================
- Coverage   61.93%   61.83%   -0.11%     
==========================================
  Files         217      217              
  Lines       15799    15799              
  Branches     2679     2679              
==========================================
- Hits         9785     9769      -16     
- Misses       5533     5545      +12     
- Partials      481      485       +4     

Flag	Coverage Δ
#unittests	61.83% <ø> (-0.11%)	⬇️

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

Impacted Files	Coverage Δ
mmdet/models/roi_heads/test_mixins.py	47.78% <0.00%> (-12.39%)	⬇️
mmdet/models/dense_heads/rpn_test_mixin.py	77.41% <0.00%> (-6.46%)	⬇️

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