Remove unnecessary permissions load

[lunny]

When a request to a route with repoassignment middleware, a permission will be loaded to ctx.Repo.Permission. So we could directly use that but not load it again.

This PR will remove these unnecessary permissions load.

[codecov-io]

Codecov Report

Merging #9796 into master will decrease coverage by 0.02%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #9796      +/-   ##
==========================================
- Coverage   42.19%   42.17%   -0.03%     
==========================================
  Files         603      603              
  Lines       78859    78862       +3     
==========================================
- Hits        33277    33258      -19     
- Misses      41507    41526      +19     
- Partials     4075     4078       +3

Impacted Files	Coverage Δ
modules/markup/markdown/goldmark.go	66.37% <0%> (-1.82%)	⬇️
services/pull/check.go	48.64% <0%> (-6.76%)	⬇️
modules/process/manager.go	74.69% <0%> (-3.62%)	⬇️
services/pull/temp_repo.go	31.62% <0%> (-2.57%)	⬇️
models/error.go	30.76% <0%> (-0.55%)	⬇️

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