fix: remove hardcoded AVM_TRANSPILER_LIB from debug CMake preset

[AztecBot]

Summary

Fixes the nightly barretenberg debug build that has been failing since 2026-03-20.

The debug CMake preset hardcoded AVM_TRANSPILER_LIB pointing to libavm_transpiler.a, but the nightly debug CI job sets AVM_TRANSPILER=0 which skips building that library. When the build cache expired (due to code changes in PR #21835), the fresh build failed at link time because the .a file doesn't exist.

Removing AVM_TRANSPILER_LIB from the debug preset lets it inherit from default (which doesn't set it), matching the CI's AVM_TRANSPILER=0 intent.

Full analysis: https://gist.github.com/AztecBot/c76c930ef9446eda7a20616035b6e60a

Test plan

• Debug build compiles (1108 targets)
• commitment_schemes_tests pass (88/88)
• ultra_honk_tests, sumcheck_tests, honk_tests, hypernova_tests, goblin_tests, flavor_tests all pass

ClaudeBox log: https://claudebox.work/s/5fc7d037bce53386?run=1