Bump extension layer to version 84 (#30980)

Author: astuyve

layouts/shortcodes/latest-lambda-layer-version.html

@@ -21,7 +21,7 @@
 
 <!-- Lambda Extension -->
 {{- if eq (.Get "layer") "extension" -}}
-    83
+    84
 {{- end -}}
 
 <!-- dd-trace-java Layer -->