Revert "back to stable toolchain"

This reverts commit 0d58d06.

Author: SteffenDE

.github/workflows/precompile.yml

@@ -45,7 +45,9 @@ jobs:
     - name: Install Rust toolchain
       uses: dtolnay/rust-toolchain@stable
       with:
-        toolchain: stable
+        # TODO: check if a later version works in the future
+        # https://elixirforum.com/t/rustler-precompiled-segfaults-in-gh-action/71189/10
+        toolchain: 1.86.0
         target: ${{ matrix.job.target }}
 
     - name: Build the project