Docs: increase maxdepth

[sdarwin]

Superproject build failing: https://app.circleci.com/pipelines/github/boostorg/boost/17254/workflows/28669b72-d706-427f-b87f-37c03add9a74

and Github actions in this repo: https://github.com/boostorg/intrusive/actions/runs/34535006999/job/103064461658

You can manually test building docs locally using the script linuxdocs.sh https://github.com/boostorg/release-tools/tree/develop/build_docs

Log output:

xslt-xsltproc /root/build/boost/bin.v2/libs/intrusive/doc/docbook/intrusive.docbook
Reference to function 'boost::intrusive::get_parent_from_member' is ambiguous. Found:
              Match in namespace ::
              Match in namespace ::
runtime error: file /root/project/tools/boostbook/xsl/source-highlight.xsl line 309 element choose
xsltApplySequenceConstructor: A potential infinite template recursion was detected.
You can adjust xsltMaxDepth (--maxdepth) in order to raise the maximum number of nested template calls and variables/params (currently set to 3000).
Templates:
#0 name highlight-text-impl-root
#1 name highlight-text-impl-root
#2 name highlight-text-impl-root
#3 name highlight-text-impl-root 

cc. @igaztanaga

[igaztanaga]

Many thanks! And I need to see why my local build was not failing...

[igaztanaga]

My local build fails with the proposed patch, so I'll need to find a new workaround.