[ST] unused tags removal: internalclients, arm arch unsupported

[henryZrncik]

Type of change

• Refactoring

Description

Removal of following Tags from System Tests:

• internalclients: as these are not used for any particular reason and were created due to now obsolete reasons which also resulted in fact that these tags were present only in fraction of all tests they were used in.
• arm64unsupported: removed as all test that were using it were from now on enabled also on this architecture (as of https://github.com/strimzi/test-clients/issues/75).

note: despite removing tag internalclients we decided to keep externalclients as these seems to be used for local testing purposes.