Fix external links in documenation
Found that a number of external links in the documentation no longer point to valid pages.
doc/advanced/external-object-storage/azure-minio-gateway.md:
[ ERROR ] external_links - broken reference to https://docs.microsoft.com/en-us/azure/azure-resource-manager/resource-group-overview: link has moved permanently to 'https://docs.microsoft.com/azure/azure-resource-manager/management/overview'
doc/advanced/geo/index.md:
[ ERROR ] external_links - broken reference to https://docs.gitlab.com/omnibus: 404
doc/architecture/decisions.md:
[ ERROR ] external_links - broken reference to https://docs.helm.sh/chart_template_guide/: link has moved permanently to 'https://helm.sh/docs/chart_template_guide/'
[ ERROR ] external_links - broken reference to https://about.gitlab.com/2017/10/11/from-dev-to-devops/: link has moved permanently to 'https://about.gitlab.com/blog/2017/10/11/from-dev-to-devops/'
doc/charts/gitlab/gitaly/index.md:
[ ERROR ] external_links - broken reference to https://docs.gitlab.com/charts/advanced/external-gitaly: 404
doc/charts/globals.md:
[ ERROR ] external_links - broken reference to https://https//github.com/helm/helm/blob/master/docs/using_helm.md: Failed to open TCP connection to https:443 (getaddrinfo: Name does not resolve)
[ ERROR ] external_links - broken reference to https://helm.sh/docs/developing_charts/: 404
doc/installation/command-line-options.md:
[ ERROR ] external_links - broken reference to https://helm.sh/docs/developing_charts/: 404
doc/installation/deployment.md:
[ ERROR ] external_links - broken reference to https://github.com/kubernetes-incubator/external-dns: link has moved permanently to 'https://github.com/kubernetes-sigs/external-dns'
doc/installation/operator.md:
[ ERROR ] external_links - broken reference to https://helm.sh/docs/developing_charts/: 404
doc/installation/tools.md:
[ ERROR ] external_links - broken reference to https://github.com/helm/helm/blob/master/docs/charts_tips_and_tricks.md: 404
[ ERROR ] external_links - broken reference to https://github.com/helm/helm/blob/master/docs/chart_template_guide/subcharts_and_globals.md: 404
[ ERROR ] external_links - broken reference to https://github.com/helm/helm/blob/master/docs/chart_template_guide/functions_and_pipelines.md: 404
[ ERROR ] external_links - broken reference to https://docs.helm.sh/using_helm/: link has moved permanently to 'https://helm.sh/docs/using_helm/'
doc/troubleshooting/index.md:
[ ERROR ] external_links - broken reference to https://gitlab.com/charts/gitlab/blob/master/doc/troubleshooting/index.md: too many redirects
Related: #1819