Fix minor typo in a comment
diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
index d2c0448..749cf6b 100644
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -1047,7 +1047,7 @@
 static int
 valid_index(Py_ssize_t i, Py_ssize_t limit)
 {
-    /* The cast to size_t let us use just a single comparison
+    /* The cast to size_t lets us use just a single comparison
        to check whether i is in the range: 0 <= i < limit */
     return (size_t) i < (size_t) limit;
 }