[fix] : remove duplicate ip's to avoid patching error

[rahulait]

General:

• Have you removed all sensitive information, including but not limited to access keys and passwords?
• Have you checked to ensure there aren't other open or closed Pull Requests for the same bug/feature/question?

We saw patch failures in CCM logs as defined below:

I1113 06:53:01.009080       1 instances.go:300] Instance kube2-control-plane-spwkz, assembled IP addresses: [{Hostname kube2-control-plane-spwkz} {InternalIP 10.0.0.2} {ExternalIP 172.232.3.128} {InternalIP 192.168.136.12} {ExternalIP 2600:3c06::f03c:95ff:feee:5519} {InternalIP 10.0.0.2} {InternalIP 192.168.136.12}]
E1113 06:53:01.020122       1 node_controller.go:404] Error patching node with cloud ip addresses = [failed to patch status "{\"status\":{\"addresses\":[{\"address\":\"kube2-control-plane-spwkz\",\"type\":\"Hostname\"},{\"address\":\"10.0.0.2\",\"type\":\"InternalIP\"},{\"address\":\"172.232.3.128\",\"type\":\"ExternalIP\"},{\"address\":\"192.168.136.12\",\"type\":\"InternalIP\"},{\"address\":\"2600:3c06::f03c:95ff:feee:5519\",\"type\":\"ExternalIP\"},{\"address\":\"10.0.0.2\",\"type\":\"InternalIP\"},{\"address\":\"192.168.136.12\",\"type\":\"InternalIP\"},{\"$patch\":\"replace\"}]}}" for node "kube2-control-plane-spwkz": Node "kube2-control-plane-spwkz" is invalid: [status.addresses[3]: Duplicate value: core.NodeAddress{Type:"InternalIP", Address:"10.0.0.2"}, status.addresses[4]: Duplicate value: core.NodeAddress{Type:"InternalIP", Address:"192.168.136.12"}]]

This PR addresses this issue and makes sure values are not duplicated.

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[codecov]

Codecov Report

Attention: Patch coverage is 81.81818% with 2 lines in your changes missing coverage. Please review.

Project coverage is 55.33%. Comparing base (1b046af) to head (38142ec).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
cloud/linode/instances.go	81.81%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #243      +/-   ##
==========================================
+ Coverage   55.30%   55.33%   +0.02%     
==========================================
  Files          12       12              
  Lines        2318     2324       +6     
==========================================
+ Hits         1282     1286       +4     
- Misses        886      887       +1     
- Partials      150      151       +1     

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