Update Infra nav (2nd iteration)

Closes #1105 (closed).

Update Infra nav:

• Remove "DEPRECATED" before each nested item (keeping only in the higher-level item).
• Update "Manage cluster applications" per gitlab#343637 (closed).
• Move "Protect deployed applications" up, after "Deploy to clusters with the CI/CD Tunnel". The "protect" nav needs to be nested into the Kubernetes main nav to follow the clusters workflow logic (install, configure, manage, deploy, protect).

BEFORE	AFTER

Notes for follow-ups:

• We may have to add Auto Deploy to the deprecated nav if it doesn't make it into 14.5 (docs are ready gitlab!73392 (closed))
• We may have to add the deprecation notice to Protect features and move them to the "deprecated features" bucket until we have the code working with the Kubernetes integration through the Agent (see gitlab-org/configure&8 (comment 728006630)).