fix(instance): use routed-ip-enabled for IP type when explicit

[Codelax]

Routed IPs are getting enabled per default.
This fix: scw instance server create with an API that enable routed_ip_enabled per default.

Before this fix, the server is created with routed_ip_enabled=true but the IP will be created as NAT because the CLI do that when routed-ip-enabled is omitted.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 75.80%. Comparing base (23ed688) to head (f940f64).

Files	Patch %	Lines
...nal/namespaces/instance/v1/custom_server_create.go	0.00%	5 Missing and 1 partial ⚠️

Additional details and impacted files

@@ Coverage Diff @@ ## master #3679 +/- ## ========================================== - Coverage 75.81% 75.80% -0.01%  ========================================== Files 190 190 Lines 42640 42641 +1 ========================================== - Hits 32327 32325 -2  - Misses 9123 9127 +4  + Partials 1190 1189 -1 

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