[CI] Part 2: Update LC3plus integration to latest ETSI release package for v.1.5.1 and re-enable job to ensure no code changes

• Requested reviewers: @kiene

Description

The check for changes job was disabled with MR !1545 (merged).

This MR re-enables the job.

This may pose an inconvenience for BASOP CI since main-pc is still on v1.4.5, next LC3plus update is in MR 157.