Stepper Component: Fix unit test

[dobanisola-scottlogic]

Describe the bug

In this Discussion . I will also look into some broken tests and where needed extend test coverage.

This issue is not a bug ticket, but simply an issue for the PR to reference.

Environment

windows

Reproducer

No response

Angular version

17.3.6

PrimeNG version

17.16.1

Build / Runtime

Angular CLI App

Language

TypeScript

Node version (for AoT issues node --version)

v21.7.3

Browser(s)

No response

Steps to reproduce the behavior

No response

Expected behavior

No response