Fix miscellaneous typos (#4275)

diff --git a/Python/ast.c b/Python/ast.c
index a6cc0f7..79cef70 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -4287,7 +4287,7 @@
 
    `parent` is the enclosing node.
    `n` is the node which locations are going to be fixed relative to parent.
-   `expr_str` is the child node's string representation, incuding braces.
+   `expr_str` is the child node's string representation, including braces.
 */
 static void
 fstring_fix_node_location(const node *parent, node *n, char *expr_str)