docs: fix default ldflag template

[leighmcculloch]

What

Change the default ldflags template that is displayed in the build docs to
show that the default sets main.commit to Commit instead of
ShortCommit.

Why

The docs state that the default ldflags includes the ShortCommit but in
reality the code uses the longer Commit value instead. This behavior has
existed since the defaults were introduced ~3 years ago in commit
4af2cb0 so even if short commit was the intended behavior, after 3 years
of it working this way we should probably just update the docs to reflect
the actual default.

Fixes #1264

[codecov-io]

Codecov Report

Merging #1265 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1265   +/-   ##
=======================================
  Coverage   83.75%   83.75%           
=======================================
  Files          58       58           
  Lines        3342     3342           
=======================================
  Hits         2799     2799           
  Misses        461      461           
  Partials       82       82

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[caarlos0]

thanks!

[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.