fix: switch to safe grpc conversion for cert

[Freyskeyd]

Description

In order to avoid panicking when malformed certificates are pushed or failure during parsing.

PR Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added or updated tests that comprehensively prove my change is effective or that my feature works

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.01% 🎉

Comparison is base (2b7517c) 57.64% compared to head (cc2691e) 57.65%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #309      +/-   ##
==========================================
+ Coverage   57.64%   57.65%   +0.01%     
==========================================
  Files         228      228              
  Lines       11807    11801       -6     
==========================================
- Hits         6806     6804       -2     
+ Misses       5001     4997       -4     

Files Changed	Coverage Δ
...topos-api/src/grpc/conversions/shared/v1/subnet.rs	36.84% <ø> (ø)
...rates/topos-api/src/grpc/conversions/uci/v1/uci.rs	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

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