fix typo

Signed-off-by: Ruihang Xia <[email protected]>

docs/rfcs/2024-02-21-multi-dimension-partition-rule/rfc.md

@@ -92,7 +92,7 @@ The data file itself can be "projected" to the key space as a polyhedron, it is
 
 ![sst-project](sst-project.png)
 
-An additional limition is that considering how the index works and how we organize the primary keys at present, the partition columns are limited to be a subset of primary keys for better performance.
+An additional limitation is that considering how the index works and how we organize the primary keys at present, the partition columns are limited to be a subset of primary keys for better performance.
 
 # Drawbacks