Remove demo UDP advertisement from Thread samples

[mspang]

Problem

This pre-SRP advertisement is not based on anything in the
specification. It dates back to 0561e68 ("[nrf5-demo] Add simple
service discovery code for nrf5 example app (#2211)") to allow discovery
prior to all of the dependencies of SRP being in place and since then
it has been copied to various other samples.

Change overview

We have SRP now, time to remove it.

Testing

Built all of the samples.
Ran nrfconnect samples & observed lack of traffic @ 5Hz.

[Damian-Nordic]

Thanks!

[github-actions]

Size increase report for "esp32-example-build" from ba12594

File	Section	File	VM
chip-temperature-measurement-app.elf	.flash.text	-56	-56

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-pigweed-app.elf and ./pull_artifact/chip-pigweed-app.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-lock-app.elf and ./pull_artifact/chip-lock-app.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-shell.elf and ./pull_artifact/chip-shell.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-all-clusters-app.elf and ./pull_artifact/chip-all-clusters-app.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-persistent-storage.elf and ./pull_artifact/chip-persistent-storage.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-temperature-measurement-app.elf and ./pull_artifact/chip-temperature-measurement-app.elf:

sections,vmsize,filesize
[Unmapped],0,56
.flash.text,-56,-56