Fixing cconv printing of function signatures with multiple tuples. (#18595)

The dreaded off-by-one.

Fixes #18594.
diff --git a/tools/iree-dump-module-main.c b/tools/iree-dump-module-main.c
index 77f1881..bee468b 100644
--- a/tools/iree-dump-module-main.c
+++ b/tools/iree-dump-module-main.c
@@ -171,7 +171,7 @@
         IREE_RETURN_IF_ERROR(iree_tooling_print_cconv_fragment(
             iree_string_view_substr(cconv_fragment, i + 1, end_pos - i - 1)));
         fprintf(stdout, ">...");
-        i = end_pos + 1;
+        i = end_pos;  // +1 from the for-loop
       } break;
       default:
         return iree_make_status(IREE_STATUS_UNIMPLEMENTED,