ci: bump asciidoc Dockerfile ruby image to 3.3.11

[Devansh-567]

Summary

docs/tools/Dockerfile.asciidoc pinned ruby:3.3.5, a stale patch release. This PR bumps it to ruby:3.3.11, the current patch tag on the 3.3.x line, to pick up upstream security fixes.

Why 3.3.11 (not 3.4.x or later)

• Stays within the same minor version (3.3.x) the image was already using, so the pinned gem versions and toolchain behavior (asciidoctor-pdf 2.3.19, asciidoctor-lists 1.1.2, the rouge build-from-source step, etc.) are unaffected.
• 3.3.11 is the latest published patch tag for ruby:3.3 on Docker Hub as of this PR.
• Jumping to 3.4.x or 4.0.x would be a larger, riskier change better suited to its own PR with dedicated toolchain testing.

Changes

One line, no other changes:

• docs/tools/Dockerfile.asciidoc: FROM ruby:3.3.5 -> FROM ruby:3.3.11

[chrispsommers]

LGTM