ci: remove CARGO_HOME override causing cross not found

The CARGO_HOME override to ${{ github.workspace }}/.cargo placed
cargo-installed binaries (like cross) in a non-PATH directory,
causing "cross: command not found" on the aarch64 build job.
Removing the override restores the default ~/.cargo which is
already on PATH in all GitHub Actions runners.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: doublegate

.github/workflows/release.yml

@@ -8,7 +8,6 @@ on:
 
 env:
   CARGO_TERM_COLOR: always
-  CARGO_HOME: ${{ github.workspace }}/.cargo
 
 permissions:
   contents: write