Pin litemap@0.7.4 for older Rust versions

Author: arik-so

ci/ci-tx-sync-tests.sh

@@ -17,6 +17,9 @@ PIN_RELEASE_DEPS # pin the release dependencies
 # Starting with version 0.5.11, the `home` crate has an MSRV of rustc 1.81.0.
 [ "$RUSTC_MINOR_VERSION" -lt 81 ] && cargo update -p home --precise "0.5.9" --verbose
 
+# Starting with version 0.7.5, the `litemap` crate has an MSRV of rustc 1.81.0.
+[ "$RUSTC_MINOR_VERSION" -lt 81 ] && cargo update -p litemap --precise "0.7.4" --verbose
+
 export RUST_BACKTRACE=1
 
 echo -e "\n\nChecking Transaction Sync Clients with features."