Change constraint_type to constraint

Update constraint keywork following https://mfix.netl.doe.gov/gitlab/exa/mfix/-/merge_requests/1360

docs/source_docs/conf.py

@@ -105,7 +105,6 @@ html_theme = 'sphinx_rtd_theme'
 #
 html_theme_options = {
     'logo_only': False,
-    'display_version': True,
     'prev_next_buttons_location': 'bottom',
     'style_external_links': False,
     'vcs_pageview_mode': '',