Update adding of google analytics key for docs

Pydata-sphinx-theme actually deprecated the top level config key
"google_analytics_id" a few releases ago, though with a standard
DeprecationWarning (which is silenced by default) so we did not catch
it.

The deprecation was expired for 0.12.0, which resulted in a warning (and
thus CircleCI reporting failure).

For more info see [the pydata-sphinx-theme docs](https://pydata-sphinx-theme.readthedocs.io/en/stable/user_guide/analytics.html).

Essentially, it is simply adding a layer of nesting for the analytics
tokens.

Author: ksunden

doc/conf.py

@@ -407,7 +407,7 @@ def js_tag_with_cache_busting(js):
 }
 include_analytics = is_release_build
 if include_analytics:
-    html_theme_options["google_analytics_id"] = "UA-55954603-1"
+    html_theme_options["analytics"] = {"google_analytics_id": "UA-55954603-1"}
 
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,