Fixing xan split help

Author: Yomguithereal

docs/cmd/split.md

@@ -3,7 +3,7 @@
 
 ```txt
 Splits the given CSV data into smaller files having a fixed number of
-rows given to -s, --size.
+rows given to -S, --size.
 
 Target file can also be split into a given number of -c/--chunks.
 

src/cmd/split.rs

@@ -9,7 +9,7 @@ use crate::CliResult;
 
 static USAGE: &str = "
 Splits the given CSV data into smaller files having a fixed number of
-rows given to -s, --size.
+rows given to -S, --size.
 
 Target file can also be split into a given number of -c/--chunks.