src: zero-initialize cap_data in node_credentials.cc

[spkapust]

Zero-initialize the cap_data array to prevent MSan warnings
about using uninitialized memory.

Signed-off-by: Sam Kapust samkapust@google.com

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.22%. Comparing base (4ee2117) to head (71647c0).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #64347      +/-   ##
==========================================
- Coverage   90.23%   90.22%   -0.01%     
==========================================
  Files         741      741              
  Lines      240979   240980       +1     
  Branches    45401    45396       -5     
==========================================
- Hits       217449   217427      -22     
+ Misses      15112    15109       -3     
- Partials     8418     8444      +26     

Files with missing lines	Coverage Δ
src/node_credentials.cc	68.43% <100.00%> (-0.25%)	⬇️

... and 24 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[hybrist]

Can you amend the commit with the fixed message? Unfortunately changing the PR title isn't sufficient to pass the check.