[Docs] Grammar Edit on Enabling HTTPS Using Reverse Proxy

[bagasme]

As per title.

This PR fix grammar errors I made from #9491.

[codecov-io]

Codecov Report

Merging #9649 into master will increase coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master   #9649      +/-   ##
=========================================
+ Coverage   42.19%   42.2%   +<.01%     
=========================================
  Files         583     583              
  Lines       77234   77234              
=========================================
+ Hits        32590   32594       +4     
+ Misses      40636   40634       -2     
+ Partials     4008    4006       -2

Impacted Files	Coverage Δ
modules/log/event.go	64.61% <0%> (-1.03%)	⬇️
models/gpg_key.go	55.59% <0%> (+0.55%)	⬆️
services/pull/merge.go	53.92% <0%> (+0.78%)	⬆️

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