[docs] Fix misaligned rowspans in Table/Bucket metrics table

[orangeCatDeveloper]

Purpose

Linked issue: #2812

The Table/Bucket table on the Monitor Metrics page renders misaligned in the current (next) docs.

The table is written as raw HTML and uses rowspan to group rows by scope/infix. Three rowspan values were left smaller than the number of rows actually in each group:

Element	rowspan	Actual rows
tabletserver (scope)	30 → 31	20 + 3 + 2 + 4 + 2
table_bucket_log (infix)	2 → 3	numSegments, startOffset, endOffset
table_bucket_remoteLog (infix)	3 → 4	numSegments, startOffset, endOffset, size

Because each group spans one row too few, the trailing rows (endOffset, size, kvSize) shift left into the wrong columns — the metric name lands under Metrics, the type under Description, and Type is left blank; kvSize even bleeds into the Scope column.

Note — this is not a duplicate of the already-merged #2813. #2813 fixed the misaligned tables as they were at that time (including the Coordinator Server table shown in the #2812 screenshot, which now renders correctly). Afterwards, the startOffset rows were added to the table_bucket_log and table_bucket_remoteLog groups without bumping their rowspan, so the Table/Bucket table broke again. #2812 is still open, and this PR fixes the remaining/regressed table that #2813 did not cover. The released docs are unaffected — the breakage is only visible in the next (development) version.

Brief change log

• Correct the rowspan counts for tabletserver, table_bucket_log, and table_bucket_remoteLog in website/docs/maintenance/observability/monitor-metrics.md.

Screenshots

Before:

After:

Tests

Docs-only change. Built the site locally (docusaurus build) with no new broken links, and verified every HTML table on the page now aligns (each rowspan matches its group's row count).

API and Format

No API or storage format changes.

Documentation

This PR is a documentation fix.