Remove sphinx_autodoc_typehints dependency

The package was only used to *remove* typehints in the documentation,
and this feature is supported natively in Sphinx as of 2.2.0 (actually
sooner, but formatting issues prevented adoption here).

CHANGELOG.md

@@ -10,7 +10,8 @@ these changes are prefixed with "**BREAKING**"
 ### Changed
 
 * `delphin.mrs.is_isomorphic()` no longer uses NetworkX
-
+* Docs no longer require the `sphinx_autodoc_typehints` package as of
+  Sphinx 2.2.0
 
 ## [v1.0.3][]
 

docs/conf.py

@@ -47,7 +47,6 @@
     'sphinx.ext.viewcode',
     'sphinx.ext.githubpages',
     'sphinx.ext.napoleon',
-    'sphinx_autodoc_typehints',
 ]
 
 # Add any paths that contain templates here, relative to this directory.
@@ -194,14 +193,8 @@
 napoleon_use_rtype = False
 
 
-# -- Options for Sphinx-Autodoc-Typehints extension --------------------------
+# -- Options for autodoc extension -------------------------------------------
 
-# see https://github.com/agronholm/sphinx-autodoc-typehints/pull/78
-# drop_type_annotations = True
+# disable type hints
 
-import sphinx_autodoc_typehints
-
-def dummy_process_docstring(app, what, name, obj, options, lines):
-    pass
-
-sphinx_autodoc_typehints.process_docstring = dummy_process_docstring
+autodoc_typehints = 'none'

docs/requirements.txt

@@ -1,4 +1,4 @@
-sphinx==2.1.2
+sphinx==2.2.0
 sphinx-rtd-theme==0.4.3
 sphinx_autodoc_typehints==1.6.0
 delphin.highlight==1.0.0