Fix typos in comments.  No changes to code.

FossilOrigin-Name: 77c692a6704cd877ba35d0afb774ab9b46364d59
diff --git a/src/expr.c b/src/expr.c
index ce3a476..ea52d66 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -1835,7 +1835,7 @@
   /* If no preexisting index is available for the IN clause
   ** and IN_INDEX_NOOP is an allowed reply
   ** and the RHS of the IN operator is a list, not a subquery
-  ** and the RHS is not contant or has two or fewer terms,
+  ** and the RHS is not constant or has two or fewer terms,
   ** then it is not worth creating an ephemeral table to evaluate
   ** the IN operator so return IN_INDEX_NOOP.
   */