skeletons: fix various typos

These typos have been fixed in the generated rspro code in
osmo-remsim.git. Fix them here as well, so when regenerating the code we
don't re-introduce the typos.

Change-Id: I9e2fa5a2e0c2bf153f67c1ae363baa1abb44f7ad
diff --git a/skeletons/constr_CHOICE.c b/skeletons/constr_CHOICE.c
index 18c24cd..6a88b29 100644
--- a/skeletons/constr_CHOICE.c
+++ b/skeletons/constr_CHOICE.c
@@ -156,7 +156,7 @@
 			}
 
 			if(ctx->left >= 0) {
-				/* ?Substracted below! */
+				/* ?Subtracted below! */
 				ctx->left += rval.consumed;
 			}
 			ADVANCE(rval.consumed);