Do not clone Kani's submodules

This is to avoid sporadic failures when trying to download the fuzzing
corpus for s2n-quic (a Kani submodule).

Author: tautschnig

scripts/run-kani.sh

@@ -132,7 +132,8 @@ setup_kani_repo() {
 
     git fetch --depth 1 origin "$commit" --quiet
     git checkout "$commit" --quiet
-    git submodule update --init --recursive --depth 1 --quiet
+    # We don't actually need any of Kani's git submodules in this repository
+    # git submodule update --init --recursive --depth 1 --quiet
     popd > /dev/null
 }