Bump version to 0.26.0 (#33)

Update action to use Kani version 0.26.0

Author: karkhaz

action.yml

@@ -38,7 +38,7 @@ runs:
     - name: Install Kani
       shell: bash
       run: |
-        export KANI_VERSION="0.25.0";
+        export KANI_VERSION="0.26.0";
         cargo install --version $KANI_VERSION --locked kani-verifier;
         cargo-kani setup;