fix(xtask.gen_syntax.typo): add s to the verb that refers to the 3d person
-//! This module generate AST datatype used by rust-analyzer.
+//! This module generates AST datatype used by rust-analyzer.
//!
//! Specifically, it generates the `SyntaxKind` enum and a number of newtype
//! wrappers around `SyntaxNode` which implement `ra_syntax::AstNode`.
