Merge pull request #3428 from privacyidea/fix_rtd_build_failures

Fix Readthedocs build process

.readthedocs.yaml

@@ -5,7 +5,6 @@
 # Required
 version: 2
 
-
 build:
   os: ubuntu-20.04
   tools: 
@@ -13,21 +12,16 @@ build:
 
 # Build html documentation in the doc/ directory with Sphinx
 sphinx:
-  builder: html
   configuration: doc/conf.py
 
-# Build HTML, PDF and ePub
+# Also build HTMLZip, PDF and ePub
+# TODO: do we need all these as well?
 formats: all
 
-# Use Python 2 to create the virtual environment, install privacyIDEA using setuptools, along with dependencies for the
-# documentation building process.  Also allow access to python packages that are globally installed by default, even if
-# they are not explicitly listed.
+# Install the pinned dependencies for the documentation building process.
 python:
   install:
     - requirements: doc/requirements.txt
-    - method: pip
-      path: .
-  system_packages: false
 
 # This is not currently needed, it is included so documentation will not break, if functionality is moved into
 # submodules.