[13853] Remove unused file that bewilder CMake find mechanism

[MiguelBarro]

The faulty scenario is the following:

> git clone https://github.com/eProsima/foonathan_memory_vendor.git
> cmake -DCMAKE_INSTALL_PREFIX="./install" -B ./foonathan_memory_vendor/build ./foonathan_memory_vendor 
> cmake --build ./foonathan_memory_vendor/build --config Release --target install 

here the CMake generator stage finds the foonathan_memory-config.cmake within the repo as a valid installation breaking the build.

Note that unfortunately the file location matches the following CMake search procedure case

<prefix>/<name>*/                                               (W)

because foonathan_memory_vendor matches foonathan_memory*.