Update GitHub docs links for SSH & GPG

[bagasme]

As per title.

The links now redirected to docs.github.com. common SSH problems link
is misredirected to Authenticating to GitHub page, so it has been
corrected to the proper troubleshooting SSH page.

Signed-off-by: Bagas Sanjaya [email protected]

[codecov-commenter]

Codecov Report

Merging #12947 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #12947      +/-   ##
==========================================
+ Coverage   42.84%   42.86%   +0.01%     
==========================================
  Files         662      662              
  Lines       73002    73002              
==========================================
+ Hits        31281    31289       +8     
+ Misses      36650    36643       -7     
+ Partials     5071     5070       -1     

Impacted Files	Coverage Δ
modules/log/file.go	73.60% <0.00%> (-1.61%)	⬇️
models/gpg_key.go	53.33% <0.00%> (-0.58%)	⬇️
services/pull/pull.go	40.78% <0.00%> (-0.50%)	⬇️
models/error.go	34.85% <0.00%> (+0.50%)	⬆️
modules/queue/workerpool.go	60.00% <0.00%> (+1.22%)	⬆️
modules/queue/unique_queue_disk_channel.go	55.38% <0.00%> (+1.53%)	⬆️
modules/indexer/stats/db.go	69.56% <0.00%> (+17.39%)	⬆️
modules/util/timer.go	85.71% <0.00%> (+42.85%)	⬆️

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