Update docs/ast-builder padding.md code block lang keyword, (gluesql#…

…1436)

Rename "rs" to "rust".
"rs" is not supported by docusaurus.

docs/docs/ast-builder/functions/text/padding.md

@@ -6,23 +6,23 @@ The AST Builder API in GlueSQL allows you to execute lpad and rpad functions for
 
 `lpad` returns the string with leading space if the length of the string is less than the specified length.
 
-```rs
+```rust
 lpad<'a, T: Into<ExprNode<'a>>>(expr: T, len: usize, fill: Option<String>) -> ExprNode<'a>
 ```
 
 ## rpad
 
 `rpad` returns the string with trailing space if the length of the string is less than the specified length.
 
-```rs
+```rust
 rpad<'a, T: Into<ExprNode<'a>>>(expr: T, len: usize, fill: Option<String>) -> ExprNode<'a>
 ```
 
 ## Examples
 
 In these examples, the LPAD and RPAD functions should return matching values.
 
-```rs
+```rust
 use {
     crate::*,
     gluesql_core::{