fix improper rendering of doxygen generated file

https://qualcomm.github.io/eld/documentation/linker_plugins/linker_plugins.html

doxygenclass: Cannot find class “eld::plugin::Plugin” in doxygen xml output for project “ELD” from directory: /home/runner/work/eld/eld/obj/tools/eld/docs/userguide/api_docs/xml