Apache mod_headers module  allows you to control request/response headers, I would check that. https://httpd.apache.org/docs/current/mod/mod_headers.html
One option is to fix this by removing this header via the Dispatcher itself. To remove it via Dispatcher:
First, enable mod_headers, by adding it to your main .conf file
LoadModule headers_module /path/to/your/lib/mod_headers.so
Following which in your .conf file add following command, where ServerName is the name of the header you want to remove from your output.
RequestHeader unset ServerName