Remove the port from the peer metrics label

[fedepaol]

Is this a BUG FIX or a FEATURE ?:

Uncomment only one, leave it on its own line:

/kind bug

/kind cleanup
/kind feature
/kind design
/kind flake
/kind failing
/kind documentation
/kind regression

What this PR does / why we need it:

For each VRF we can have only one neighbor for a given address, which makes the port irrelevant.

Additionally, now that frr-k8s can accept connections too, the port can either be the one used on our side to establish the connection, or the source port in case we are accepting a bgp connection. This makes the metric labels non predictable and hard to monitor.

Because of this, here we remove the port from the label.

Special notes for your reviewer:

Release note:

The BGP metrics label corresponding to the peer does not have the port anymore. Because now FRR-K8S allow incoming connections, the port might be source port of the tcp connection, making the metrics label not reliable. Additionally, we can only have one peer per VRF, so the port is not relevant.