Revert "build: add an initial CMake based build system for DocC (#818)"

CONTRIBUTING.md

@@ -350,32 +350,7 @@ by running the test suite in a Docker environment that simulates Swift on Linux.
     cd swift-docc
     swift run docc
     ```
-
-## Updating Build Rules
-
-In order to build DocC as part of the Windows toolchain distribution uniformly,
-a parallel CMake based build exists. Note that this is **not** supported for
-development purposes (you cannot execute the test suite with this build).
-
-CMake requires that the full file list is kept up-to-date. When adding or
-removing files in a given module, the `CMakeLists.txt` list must be updated to
-the file list.
-
-The 1-line script below lists all the Swift files in the current directory tree. 
-You can use the script's output to replace the list of files in the CMakeLists.txt file for each target that you added files to or removed files from.
-
-```bash
-python -c "print('\n'.join((f'{chr(34)}{path}{chr(34)}' if ' ' in path else path) for path in sorted(str(path) for path in __import__('pathlib').Path('.').rglob('*.swift'))))"
-```
-
-This should provide the listing of files in the module that can be used to
-update the `CMakeLists.txt` associated with the target.
-
-In the case that a new target is added to the project, the new directory would
-need to add the new library or executable target (`add_library` and
-`add_executable` respectively) and the new target subdirectory must be listed in
-the `Sources/CMakeLists.txt` (via `add_subdirectory`).
-
+    
 ## Continuous Integration
 
 Swift-DocC uses [swift-ci](https://ci.swift.org) infrastructure for its continuous integration