[MNT-24682] Kerberos: do not add authorization header

Please check if the PR fulfills these requirements

[x] The commit message follows our guidelines

[x] Tests for the changes have been added (for bug fixes / features)

[ ] Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (check one with "x")

[x] Bugfix

[ ] Feature

[ ] Code style update (formatting, local variables)

[ ] Refactoring (no functional changes, no api changes)

[ ] Build related changes

[ ] Documentation

[ ] Other... Please describe:

What is the current behaviour? (You can also link to an open issue here)

When Kerberos is enabled, the Authorization header is being sent with basic authentication making some requests to fail with 401 error.

Further information can be found in MNT-24642 namely the comparison between sending and not sending the header with Kerberos.

What is the new behaviour?

Prevent the header from being added to the request if Kerberos is enabled.

Does this PR introduce a breaking change? (check one with "x")

[ ] Yes

[x] No

If this PR contains a breaking change, please describe the impact and migration path for existing applications: ...

Other information:

Two notes regarding the unit test I have added to authentication.service.spec.ts:

Tests are not being executed since xdescribe is being used (I had to change to describe locally in order to run my test)
I also had to change BasicAlfrescoAuthService.getTicketEcmBase64 access modifier in order to mock/verify it in my test

Alfresco / alfresco-ng2-components

[MNT-24682] Kerberos: do not add authorization header #10320

Quality Gate passed