doc/rados: Fix minor issues, improvements in health-checks.rst (4 of x)

doc/rados: Fix minor issues, improvements in health-checks.rst (4 of x)

Remove spaces at the end of lines.

Use title case consistently in section titles.

Use confval instead of simple inline literal text for config values.

Use a privileged prompt for CLI command examples requiring privileges.

Change few last double spaces after full stop to a single space.

Use double backticks consistently for literals.

Linkify mentions of other sections in the document.

Linkify, adding a label in the destination if necessary:
- Muting health checks

Remove hyphen from "RGW-bucket index objects".

Capitalize example health warning always same as the actual message.

Promptify few remaining CLI example commands using literal text.
Use console code-block for CLI outputs to avoid highlighting.

Signed-off-by: Ville Ojamo <git2233+ceph@ojamo.eu>