doc: call Python build script as a pre_build job

RTD now supports adding extra commands [1] as jobs to run during
different parts of the build stage. This can be used to call the Python
build script instead of (ab)using RTD's setup.py support.

[1]: https://docs.readthedocs.io/en/stable/config-file/v2.html#build-jobs

.readthedocs.yaml

@@ -6,14 +6,13 @@ build:
     - swig
   tools:
     python: "3.11"
+  jobs:
+    pre_build:
+      - python doc/rtd_build.py
 
 python:
   install:
     - requirements: doc/requirements.txt
-    # the 'setuptools' method calls doc/setup.py that configures files and runs doxygen
-    # the 'pip' method doesn't work this way
-    - method: setuptools
-      path: doc
 
 sphinx:
   builder: html

doc/rtd_build.py

@@ -74,5 +74,3 @@ generate_bindings_from_dir(os.path.join(
 generate_bindings_from_dir(os.path.join(DIR + "/../bindings/libdnf5_cli"),
                            os.path.join(DIR + "/../bindings/python3/libdnf5_cli"))
 
-# no setup() is called
-# this file only configures files for building docs in Read the Docs