Remove some autotools leftovers (#11916)

Follow-up on 332fe3c

Author: raboof

README.md

@@ -151,8 +151,6 @@ trafficserver ............. Top src dir
 ├── lib ...................
 │   ├── records ........... Library for config files
 │   └── yamlcpp ........... Library for YAML of C++
-├── m4 .................... Custom macros for configure.ac
-├── mk .................... Includes for Makefiles
 ├── mgmt .................. JSONRPC server/management and tools
 ├── plugins ............... Stable core plugins
 │   └── experimental ...... Experimental core plugins