Remove: 删除过时的 Export 功能

[yanyongyu]

fix #935

[codecov]

Codecov Report

Merging #1125 (5397323) into master (e5e69c2) will decrease coverage by 0.08%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1125      +/-   ##
==========================================
- Coverage   78.70%   78.62%   -0.09%     
==========================================
  Files          42       41       -1     
  Lines        3189     3162      -27     
==========================================
- Hits         2510     2486      -24     
+ Misses        679      676       -3     

Flag	Coverage Δ
unittests	78.62% <100.00%> (-0.09%)	⬇️

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

Impacted Files	Coverage Δ
nonebot/__init__.py	100.00% <ø> (ø)
nonebot/plugin/__init__.py	96.61% <ø> (-0.12%)	⬇️
nonebot/plugin/plugin.py	100.00% <ø> (ø)
nonebot/plugin/load.py	58.33% <100.00%> (ø)
nonebot/plugin/manager.py	94.53% <0.00%> (+0.78%)	⬆️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[github-actions]

🚀 Deployed on https://deploy-preview-1125--nonebot2.netlify.app