Remove JavaScript metrics docs and update related links and redirects

Co-authored-by: cody.dearkland <[email protected]>

Author: cursoragent

docs/platforms/javascript/common/metrics/index.mdx

@@ -3,7 +3,7 @@
 - [Dart (version `6.11.0` or later)](/platforms/dart/performance/instrumentation/performance-metrics/)
 - [Flutter (version `6.11.0` or later)](/platforms/dart/guides/flutter/performance/instrumentation/performance-metrics/)
 - [Java (version `6.5.0` or later)](/platforms/java/performance/instrumentation/performance-metrics/)
-- [JavaScript (version `7.0.0` or later)](/platforms/javascript/performance/instrumentation/performance-metrics/)
+- [JavaScript (version `7.0.0` or later)](/platforms/javascript/tracing/span-metrics/)
 - [.NET (version `3.23.0` or later)](/platforms/dotnet/performance/instrumentation/performance-metrics/)
 - [Python (version `1.5.12` or later)](/platforms/python/tracing/instrumentation/custom-instrumentation/)
 - [React Native (version `4.0.0` or later)](/platforms/react-native/performance/instrumentation/performance-metrics/)

includes/custom-measurements-supported-sdks.mdx

@@ -1068,6 +1068,14 @@ const userDocsRedirects = [
     source: '/platforms/javascript/tracing/trace-propagation/:path*',
     destination: '/platforms/javascript/tracing/distributed-tracing/:path*',
   },
+  {
+    source: '/platforms/javascript/metrics',
+    destination: '/platforms/javascript/tracing/span-metrics/',
+  },
+  {
+    source: '/platforms/javascript/guides/:guide/metrics',
+    destination: '/platforms/javascript/guides/:guide/tracing/span-metrics/',
+  },
   {
     source: '/platforms/javascript/tracing/instrumentation/performance-metrics/',
     destination: '/platforms/javascript/tracing/span-metrics/',