Regex for bgp-large-community-type is broken

[mjethanandani]

Issue reported by Maria Matekja on this thread - https://mailarchive.ietf.org/arch/msg/idr/3rVyYyqVHIy9lMk12CPobFJ3CSo/

Regex on pages 112-113 representing bgp-large-community-type doesn't match 4199999999:0:0 which is an obvious bug. Our suggestion is to make it a container:

container bgp-large-community {
leaf asn { type uint32; }
leaf data1 { type uint32; }
leaf data2 { type uint32; }
}

This also aligns better with RFC 8092 where the large community is defined as a block of three uint32 values.

[mjethanandani]

Fix the regex. Rest is up for discussion.