fix: allow insecure connections with subxt

[dandanlen]

Included in 1.7.4 release already: #5478

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.

Project coverage is 72%. Comparing base (86c4e99) to head (d10b385).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
engine/src/dot/rpc.rs	0%	8 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff           @@
##            main   #5479    +/-   ##
======================================
- Coverage     72%     72%    -0%     
======================================
  Files        494     494            
  Lines      88073   87955   -118     
  Branches   88073   87955   -118     
======================================
- Hits       63189   63011   -178     
- Misses     22304   22363    +59     
- Partials    2580    2581     +1     

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