Fix downloads url

[johanvdw]

The link without slash is not working.

[codecov-io]

Codecov Report

Merging #8153 into master will increase coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #8153      +/-   ##
==========================================
+ Coverage   41.82%   41.82%   +<.01%     
==========================================
  Files         482      482              
  Lines       64583    64583              
==========================================
+ Hits        27014    27015       +1     
+ Misses      34099    34096       -3     
- Partials     3470     3472       +2

Impacted Files	Coverage Δ
modules/log/file.go	75.52% <0%> (-2.1%)	⬇️
models/repo_list.go	73.17% <0%> (-0.98%)	⬇️
routers/repo/view.go	43.54% <0%> (+1.01%)	⬆️
models/unit.go	67.56% <0%> (+5.4%)	⬆️

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[techknowlogick]

Thanks for docs update :)