Fix a compile error caused by a bug in parity-db crate:
error: failed to parse manifest at `[..]/parity-db-0.2.3/Cargo.toml`
Caused by:
failed to parse the version requirement `0.11 ` for dependency `parking_lot`
Caused by:
expected comma after minor version number, found '\t'
Fix a compile error caused by a bug in parity-db crate: