DOCS-1789 - Consolidate Mobot monitor-creation docs, fix sidebar label

[kimsauce]

Purpose of this pull request

create-monitor-with-mobot.md was published as a standalone page with no cross-reference from create-monitor.md, unlike every other alternate monitor-creation method (Terraform, dashboard/log-search entry points), which are cross-linked from the main doc rather than left to stand alone. It also has a sidebar_label plural mismatch with its sibling doc, and mobot/index.md's "Conversational Monitors" section duplicates most of its content instead of teasing it.

This PR:

• Adds a "Using Mobot" entry under create-monitor.md's Other configurations, mirroring the existing "Using Terraform" pattern.
• Renames create-monitor-with-mobot.md's sidebar_label from "Create Monitors with Mobot" to "Create a Monitor with Mobot", matching the singular phrasing of its sibling "Create a New Monitor."
• Trims mobot/index.md's Conversational Monitors section to a short teaser, removing bullet lists (starting inputs, adjustable defaults, known limitations) that duplicated the dedicated doc — cutting the two-places-to-update problem down to one.

Not touched: create-monitor-with-mobot.md's own content, which is well-organized and just needed better cross-linking, not restructuring.

Select the type of change

• Minor Changes - Typos, formatting, slight revisions
• Update Content - Revisions, updating sections
• New Content - New features, sections, pages, tutorials
• Site and Tools - .clabot, version updates, maintenance, dependencies, new packages for the site (Docusaurus, Gatsby, React, etc.)

Ticket (if applicable)

https://sumologic.atlassian.net/browse/DOCS-1789

[JV0812]

Good consolidation — verified the dedicated Mobot doc already covers everything trimmed from mobot/index.md (monitor limitations, example prompts, FAQ), so no info is lost. The "Using Mobot" section mirrors the existing "Using Terraform" pattern correctly.

One thing to fix before merge: the sidebar_label rename on create-monitor-with-mobot.md isn't matched by a title update, so the sidebar nav will say "Create a Monitor with Mobot" while the page's own H1 still renders "Create Monitors with Mobot." The two new/updated links in this PR (from create-monitor.md and mobot/index.md) also use the new singular phrasing, so readers will click through to a page whose heading doesn't match what they clicked. See inline comment.

[JV0812]

Title/sidebar_label mismatch resolved — title now reads "Create a Monitor with Mobot" and matches the sidebar_label used in the new cross-links. LGTM.