Fix example in PLE1520 documentation (#13210)

Author: Jinior

crates/ruff_linter/src/rules/pylint/rules/singledispatchmethod_function.rs

@@ -30,7 +30,7 @@ use crate::importer::ImportRequest;
 /// Use instead:
 ///
 /// ```python
-/// from functools import singledispatchmethod
+/// from functools import singledispatch
 ///
 ///
 /// @singledispatch