[docs] Support redirect of placeholder-page paths to their targets (#3401)

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

website_docs/api.md

@@ -1,9 +1,7 @@
 ---
 title: API reference
 linkTitle: API
-# Note: this is a placeholder page. Attempting to visit this page will
-# redirect to the following URL:
-manualLink: https://pkg.go.dev/go.opentelemetry.io/otel
+redirect: https://pkg.go.dev/go.opentelemetry.io/otel
 manualLinkTarget: _blank
 _build: { render: link }
 weight: 50

website_docs/examples.md

@@ -1,8 +1,6 @@
 ---
 title: Examples
-# Note: this is a placeholder page. Attempting to visit this page will
-# redirect to the following URL:
-manualLink: https://github.com/open-telemetry/opentelemetry-go/tree/main/example
+redirect: https://github.com/open-telemetry/opentelemetry-go/tree/main/example
 manualLinkTarget: _blank
 _build: { render: link }
 weight: 60