Compilation warning from docbook code

[Pavel Sanda]

On Mon, Jun 29, 2020 at 10:48:04AM -0400, Scott Kostyshak wrote:
> I get the following warning on current master:
> 
>   [ 93%] Building CXX object src/CMakeFiles/lyx.dir/output_docbook.cpp.o
>   44:19: warning: ???const string lyx::{anonymous}::fontToDocBookTag(lyx::xml::FontTypes)??? defined but not used [-Wunused-function]
>      44 | std::string const fontToDocBookTag(xml::FontTypes type) {
>         |                   ^~~~~~~~~~~~~~~~
> 
> By the way, thanks to Thibaut and Pavel for the work.

I would not worry about those until the whole codebase is imported. P