Remove etcd v2

docs/configuration/backends/etcd.md

@@ -31,16 +31,6 @@ watch = true
 #
 prefix = "/traefik"
 
-# Force to use API V3 (otherwise still use API V2)
-#
-# Deprecated
-#
-# Optional
-# Default: false
-#
-useAPIV3 = true
-
-
 # Override default configuration template.
 # For advanced users :)
 #
@@ -69,7 +59,3 @@ useAPIV3 = true
 To enable constraints see [provider-specific constraints section](/configuration/commons/#provider-specific).
 
 Please refer to the [Key Value storage structure](/user-guide/kv-config/#key-value-storage-structure) section to get documentation on Traefik KV structure.
-
-!!! note
-    The option `useAPIV3` allows using Etcd API V3 only if it's set to true.
-    This option is **deprecated** and API V2 won't be supported in the future.

docs/user-guide/kv-config.md

@@ -370,10 +370,6 @@ As a result, it may be possible for Træfik to read an intermediate configuratio
 To solve this problem, Træfik supports a special key called `/traefik/alias`.
 If set, Træfik use the value as an alternative key prefix.
 
-!!! note
-    The field `useAPIV3` allows using Etcd V3 API which should support updating multiple keys atomically with Etcd.
-    Etcd API V2 is deprecated and, in the future, Træfik will support API V3 by default.
-
 Given the key structure below, Træfik will use the `http://172.17.0.2:80` as its only backend (frontend keys have been omitted for brevity).
 
 | Key                                                                     | Value                       |