Fix versioning (#20285)

Author: guardrex

aspnetcore/fundamentals/servers/kestrel.md

@@ -340,6 +340,8 @@ webBuilder.ConfigureKestrel(serverOptions =>
 
 The default value is 96 KB (98,304).
 
+::: moniker-end
+
 ::: moniker range=">= aspnetcore-5.0"
 
 ### HTTP/2 keep alive ping configuration
@@ -364,6 +366,8 @@ webBuilder.ConfigureKestrel(serverOptions =>
 
 ::: moniker-end
 
+::: moniker range=">= aspnetcore-3.0"
+
 ### Trailers
 
 [!INCLUDE[](~/includes/trailers.md)]