NethVoice CTI: Operator panel favorite label is inverted

[mgarra]

Description:
In the NethCTI operator panel, the label associated with the favorite setting for extensions is reversed.

• When an extension is not marked as a favorite (i.e. the favorite is to be added), the icon is correct (a hollow star), but the label incorrectly says:
  "Remove favorite operator"
  instead of
  "Set as favorite operator".

• When an extension is already marked as a favorite, the icon is also correct, but the label incorrectly says:
  "Set as favorite operator"
  instead of
  "Remove favorite operator".

Expected behavior:
The labels should be inverted:

For non-favorite extensions → “Set as favorite operator”

For favorite extensions → “Remove favorite operator”

Summary:
Only the labels need to be swapped to match the actual state and icon of the favorite button.

[edospadoni]

Testing release:

• https://github.com/nethesis/ns8-nethvoice/releases/tag/1.5.1-testing.4

[edospadoni]

Test case:

• check the bug is not reproducible