mod_http2: remove the no longer existing h2_ngn_shed.c from Cmake.

trunk patch: http://svn.apache.org/r1856910
2.4.x patch: svn merge -c 1856910 ^/httpd/httpd/trunk .
+1: icing, covener, ylavic


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1860127 13f79535-47bb-0310-9956-ffa450edef68