Fix minor format stnank with genast.py

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

tools/genast.py

@@ -88,7 +88,7 @@ def define_ast(wr: FileWriter, base: str, type_lines: list[str]):
         wr.line()
         wr.line(f"impl {base} for {type}{base} " + "{")
         wr.line(
-            f"    fn accept(&self, visitor: &mut dyn {visitor}) -> Result<(), Box<dyn std::error::Error>>"
+            f"    fn accept(&self, visitor: &mut dyn {visitor}) -> Result<(), Box<dyn std::error::Error>> "
             + "{"
         )
         wr.line(f"        visitor.visit_{type.lower()}_{base.lower()}(self)")