Fix bgp as format resource and data source

Author: danischm

docs/resources/bgp_as_format.md

@@ -14,6 +14,7 @@ This resource can manage the BGP AS Format configuration.
 
 ```terraform
 resource "iosxr_bgp_as_format" "example" {
+  as_format = "asplain"
 }
 ```
 

examples/resources/iosxr_bgp_as_format/resource.tf

@@ -1,2 +1,3 @@
 resource "iosxr_bgp_as_format" "example" {
+  as_format = "asplain"
 }

gen/definitions/bgp_as_format.yaml

@@ -4,13 +4,11 @@ path: Cisco-IOS-XR-um-router-bgp-cfg:/as-format
 doc_category: BGP
 skip_minimum_test: true
 attributes:
-  - yang_name: ""
-    tf_name: "as_format"
+  - yang_name: as-format
+    tf_name: as_format
     type: String
     no_augment_config: true
-    optional: true
-    example: "asplain"
+    example: asplain
     enum_values:
-      - "asdot"
-      - "asplain"
-    exclude_test: true
+      - asdot
+      - asplain