docs: fix broken links

[sh0rez]

Several links were using a path format not understood by Hugo, which
renders these docs at https://grafana.com/docs/loki/latest.

To avoid 404s, these are now adapted.

[codecov-commenter]

Codecov Report

Merging #2595 into master will decrease coverage by 0.07%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2595      +/-   ##
==========================================
- Coverage   63.03%   62.95%   -0.08%     
==========================================
  Files         169      169              
  Lines       15015    15015              
==========================================
- Hits         9464     9452      -12     
- Misses       4792     4806      +14     
+ Partials      759      757       -2     

Impacted Files	Coverage Δ
pkg/promtail/positions/positions.go	46.49% <0.00%> (-13.16%)	⬇️
pkg/logql/evaluator.go	92.88% <0.00%> (+0.40%)	⬆️
pkg/promtail/targets/file/filetarget.go	66.85% <0.00%> (+0.57%)	⬆️