don't check external network existence when swarm is enabled

[ndeloof]

What I did
we can't check a swarm overlay network exists until we connect a container. Asking user to declare driver: overlay is conter-intuitive and incorrect (an external resource should have no config element declared). Better ignore and wait for connect API call to (maybe) fail and report an error to user.

Related issue
fixes #11387

(not mandatory) A picture of a cute animal, if possible in relation to what you did

[codecov]

Codecov Report

Attention: 7 lines in your changes are missing coverage. Please review.

Comparison is base (8c80297) 56.54% compared to head (84796d4) 56.54%.
Report is 3 commits behind head on main.

❗ Current head 84796d4 differs from pull request most recent head da1a34a. Consider uploading reports for the commit da1a34a to get more accurate results

Files	Patch %	Lines
pkg/compose/create.go	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11409      +/-   ##
==========================================
- Coverage   56.54%   56.54%   -0.01%     
==========================================
  Files         136      136              
  Lines       11545    11542       -3     
==========================================
- Hits         6528     6526       -2     
  Misses       4390     4390              
+ Partials      627      626       -1     

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