update package doc

Cargo.toml

@@ -15,9 +15,7 @@ threads = ["tokio/rt-threaded"]
 # Use base64 encoding of pathnames instead of SHA256. This can increase speed of database rebuilding, but can also cause files with large pathnames to fail.
 fast-pathnames = ["base64"]
 
-# Use low-precision argument dedup (64-bit) instead of high (unimplemented)
-#
-# Currently does nothing as this is the default and only implemented one.
+# Use low-precision argument dedup (64-bit hash) instead of high (256-bit hash)
 low-prec-arg-dedup = []
 
 [dependencies]