Administration guide: update content for devworkspace, in the master branch

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Administration guide to document only instances with devworkspace.

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Administration guide: update content for features on instances with devworkspace, in the master branch.

Here is the current list of the admin guide articles with in bold the ones to update:

• architecutre-overview
  • architecture-overview [WONT FIX for 3.0]
• calculating-che-resource-requirements @ibuziuk https://github.com/eclipse-che/che-docs/pull/2270
• retrieving-che-logs
  • configuring-server-logging
  • collecting-logs-using-chectl @amisevsk https://github.com/eclipse-che/che-docs/pull/2263
• monitoring-che @dkwon17 https://github.com/eclipse-che/che-docs/pull/2279
• monitoring-the-dev-workspace-operator @dkwon17 https://github.com/eclipse-che/che-docs/pull/2276
• caching-images-for-faster-workspace-start @ibuziuk https://github.com/eclipse-che/che-docs/pull/2258
• managing-identities-and-authorizations
  • removing-user-data @ibuziuk https://github.com/eclipse-che/che-docs/pull/2278
  • https://github.com/eclipse/che/issues/21330

[ibuziuk]

All sub-tasks have been done and all PRs have been merged in master. Closing

[pmkovar]

One more update to the assignments:

@Eva-Lotte x @ibuziuk