ci: add missing comment explaining singlethreaded avm testing (#1762)

.github/workflows/tests.yaml

@@ -37,6 +37,7 @@ jobs:
       - run: cargo fmt -- --check
       - run: cargo clippy --all-targets -- -D warnings
       - run: cargo test
+      # using singlethreaded testing for avm so that tests that change files do not conflict with each other
       - run: cd avm && cargo fmt -- --check && cargo clippy --all-targets -- -D warnings && cargo test -- --test-threads=1
       - run: cd ts && yarn --frozen-lockfile
       - run: cd ts && yarn test