interpreter: fix int64 format in ptr dtypes

[superlopuh]

There is currently a bug, I used the wrong struct code for the encoding of int64.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.85%. Comparing base (996f649) to head (a396883).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3035      +/-   ##
==========================================
- Coverage   89.85%   89.85%   -0.01%     
==========================================
  Files         413      414       +1     
  Lines       51852    51872      +20     
  Branches     8006     8009       +3     
==========================================
+ Hits        46592    46608      +16     
- Misses       3970     3973       +3     
- Partials     1290     1291       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.