Upgrade rust to latest stable

Author: Mauro Lacy

.github/workflows/local-tests.yml

@@ -9,7 +9,7 @@ jobs:
   local-build-test:
     runs-on: ubuntu-latest
     container:
-      image: rust:1.78.0
+      image: rust:1.86.0
     steps:
     - uses: actions/[email protected]
     - name: Build contracts, check formats, and run unit tests