Remove 'exclude-filter' from telemetry model

[earies]

• Remnants from original YANG subscribe RPC that did not carry over to gNMI so no support for dynamic subscriptions
• No definition of filter language for opaque string value w/ marking for possible removal added some time back

[OpenConfigBot]

Compatibility Report for commit e0a66ed75f3e108b35f253344a24f93b8d2ea518: ⛔ yanglint@SO 1.10.17

[earies]

Leaving out semver changes in the case changes are aggregated prior to publish

[robshakir]

I think there's a bigger conversation to have here - given that we have moved on quite significantly from the model that this describes. I'd propose that we look at what else needs to be removed from this module.

@gcsl - thoughts here?