[TASK] Align navigation item names with their corresponding page headers

[jenny-s51]

Description

Acceptance Criteria

1. The navigation item "Workspace kinds" leads to a page with the header "Kubeflow Workspace Kinds".

   Suggestion: Change the page header to "Workspace kinds" as "Kubeflow" is redundant in this context.

2. The navigation item "Notebooks" leads to a page with the header "Kubeflow Workspaces".

   Suggestion: Decide on a single term ("Notebooks" or "Workspaces") and use it consistently for both the navigation item and the page header.

[jenny-s51]

/assign