small: eliminate unused variable warn on clang 15

Bump the small submodule with the following commit:

* https://github.com/tarantool/small/commit/5c3a0880ae4659cb662085563ff0b9eee40565fe

See https://github.com/tarantool/small/issues/57
Part of #8110

NO_DOC=build fix
NO_TEST=build fix
NO_CHANGELOG=to be added in a commit that fixes #8110

small @ 5c3a0880

-Subproject commit c1ac3eef79a7394fb52442a77b958b66d82b8f0b
+Subproject commit 5c3a0880ae4659cb662085563ff0b9eee40565fe