Sentence-case package registry in docs

doc/administration/geo/replication/datatypes.md

doc/administration/geo/replication/troubleshooting.md

doc/administration/instance_limits.md

doc/administration/maintenance_mode/index.md

doc/administration/packages/index.md

doc/administration/settings/continuous_integration.md

doc/administration/settings/package_registry_rate_limits.md

doc/administration/settings/rate_limits.md

doc/api/packages/composer.md

doc/api/packages/npm.md

doc/api/packages/nuget.md

doc/api/packages/pypi.md

doc/api/settings.md

doc/ci/examples/index.md

doc/ci/examples/semantic-release.md

doc/ci/jobs/ci_job_token.md

doc/ci/yaml/signing_examples.md

doc/development/fe_guide/registry_architecture.md

doc/development/packages/new_format_development.md

doc/development/packages/settings.md