Deprecate configuration related to git_trace_log_file

Summary

Currently gitlab-shell no longer support actions related to git_trace_log_file. Code related to git_trace_log_file in gitlab-shell@0b4fd0af has long gone by now.

See gitaly#1300 (closed) for reference of removal commit

Steps to reproduce

>rg git_trace_log_file
files/gitlab-config-template/gitlab.rb.template
804:# gitlab_shell['git_trace_log_file'] = "/var/log/gitlab/gitlab-shell/gitlab-shell-git-trace.log"

spec/chef/recipes/gitlab-shell_spec.rb
89:                       git_trace_log_file: '/tmp/log/gitlab-shell-git-trace.log'
97:          git_trace_log_file: '/tmp/log/gitlab-shell-git-trace.log'

files/gitlab-cookbooks/gitlab/attributes/default.rb
448:default['gitlab']['gitlab-shell']['git_trace_log_file'] = nil

files/gitlab-cookbooks/gitlab/recipes/gitlab-shell.rb
76:              git_trace_log_file: node['gitlab']['gitlab-shell']['git_trace_log_file'],

files/gitlab-cookbooks/gitlab/templates/default/gitlab-shell-config.yml.erb
43:<% if @git_trace_log_file %>
49:git_trace_log_file: "<%= @git_trace_log_file %>"

What is the current bug behavior?

Poor documentation and confusing configuration

What is the expected correct behavior?

References related to this settings should be removed together with the code in gitlab-shell