Improve migration guide

Co-authored-by: Baptiste Mayelle <baptiste.mayelle@traefik.io>

docs/content/reference/static-configuration/cli-ref.md

@@ -201,9 +201,6 @@ WriteTimeout is the maximum duration before timing out writes of the response. I
 `--entrypoints.<name>.udp.timeout`:  
 Timeout defines how long to wait on an idle session before releasing the related resources. (Default: ```3```)
 
-`--experimental.http3`:  
-Enable HTTP3. (Default: ```false```)
-
 `--experimental.kubernetesgateway`:  
 Allow the Kubernetes gateway api provider usage. (Default: ```false```)
 

docs/content/reference/static-configuration/env-ref.md

@@ -201,9 +201,6 @@ WriteTimeout is the maximum duration before timing out writes of the response. I
 `TRAEFIK_ENTRYPOINTS_<NAME>_UDP_TIMEOUT`:  
 Timeout defines how long to wait on an idle session before releasing the related resources. (Default: ```3```)
 
-`TRAEFIK_EXPERIMENTAL_HTTP3`:  
-Enable HTTP3. (Default: ```false```)
-
 `TRAEFIK_EXPERIMENTAL_KUBERNETESGATEWAY`:  
 Allow the Kubernetes gateway api provider usage. (Default: ```false```)
 

docs/content/reference/static-configuration/file.toml

@@ -459,7 +459,6 @@
 
 [experimental]
   kubernetesGateway = true
-  http3 = true
   [experimental.plugins]
     [experimental.plugins.Descriptor0]
       moduleName = "foobar"

docs/content/reference/static-configuration/file.yaml

@@ -489,7 +489,6 @@ certificatesResolvers:
     tailscale: {}
 experimental:
   kubernetesGateway: true
-  http3: true
   plugins:
     Descriptor0:
       moduleName: foobar