Replace HTML theme options url with main conf.py setting

conf.py

@@ -22,6 +22,7 @@
 project = u'Agaric Technology Collective'
 copyright = u'2006—2024, Agaric, LLC'
 author = u'Benjamin Melançon, Michele Metts, Christopher Thompson, Mauricio Dinarte, David Valdez, Clayton Dewey'
+html_baseurl = 'https://docs.agaric.coop/'
 
 # The short X.Y version
 version = u''
@@ -101,7 +102,6 @@ html_css_files = [
 # TIP: If it starts with `html_` it belongs directly as a conf.py option and
 # NOT in html_theme_options.
 html_theme_options = {
-    'html_baseurl': 'https://docs.agaric.coop/',
     'logo_only': True,
 }