Don't use parking_lot versions newer than 0.12.4

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

Author: simonwuelker

Cargo.toml

@@ -36,6 +36,12 @@ string_cache = "0.9.0"
 string_cache_codegen = "0.6.1"
 utf-8 = "0.7"
 
+# These are transitive dependencies, but we need to pin them here because
+# their newer versions bump the MSRV past our MSRV (1.70 at the time of writing).
+parking_lot = ">= 0.12, < 0.12.5"
+parking_lot_core = ">= 0.9, < 0.9.12"
+lock_api = ">= 0.4, < 0.4.14"
+
 # Dev dependencies
 criterion = "0.7"
 env_logger = "0.10"