Revert "Use gtag.js analytics library for all site tags"

This reverts commit c7c3fa7.

layouts/partials/head.html

@@ -45,9 +45,8 @@
 
 {{/* To comply with GDPR, cookie consent scripts places in head-end must execute before Google Analytics is enabled */ -}}
 {{ if hugo.IsProduction -}}
-  {{ $enableGtagForUniversalAnalytics := not .Site.Params.disableGtagForUniversalAnalytics -}}
-  {{ if (or $enableGtagForUniversalAnalytics (hasPrefix .Site.GoogleAnalytics "G-")) -}}
-    {{ template "_internal/google_analytics_gtag.html" . -}}
+  {{ if hasPrefix .Site.GoogleAnalytics "G-" -}}
+    {{ template "_internal/google_analytics.html" . -}}
   {{ else -}}
     {{ template "_internal/google_analytics_async.html" . -}}
   {{ end -}}

userguide/content/en/docs/adding-content/feedback.md

@@ -33,11 +33,6 @@ started** section of [Introducing Google Analytics 4 (GA4)][ga4-intro].
 Enable Google Analytics by adding your project's analytics ID to the site
 configuration file. For details, see [Configure Google Analytics][].
 
-By default, Docsy uses the [gtag.js][] analytics library for both GA4 (which
-_requires_ `gtag.js`) and Universal Analytics (UA) site tags. If you prefer using
-the older `analytics.js` library for your UA site tag, then set
-`params.disableGtagForUniversalAnalytics` to false in your project's config.
-
 {{% alert title="Warning" color="warning" %}}
   <!-- Remove this warning once the Hugo docs have been updated to include it. -->
 
@@ -294,7 +289,6 @@ partial. For details, see [Customizing templates]({{< ref "lookandfeel#customizi
 [Configure Google Analytics]: https://gohugo.io/templates/internal/#configure-google-analytics
 [ga4-intro]: https://support.google.com/analytics/answer/1042508
 [Google Analytics]: https://analytics.google.com/analytics/web/
-[gtag.js]: https://support.google.com/analytics/answer/10220869
 [hugo-ga]: https://gohugo.io/templates/internal/#google-analytics
 [internal templates]: https://gohugo.io/templates/internal/
 [layouts/partials/page-description.html]: https://github.com/google/docsy/blob/main/layouts/partials/page-description.html