Fix smallvec dependency conflict

[ckoopmann]

Currently when trying to install reth as a library, there is an error due to conflicting nested dependencies on the `smallvec package. (See this ci failure).

This pr in it's current version fixes that specific conflict, which however uncovers another conflict regarding "bitflags". (see this other ci failure).

This leads me to wonder wether I am doing something wrong when importing reth like this, or if not wether there is something else that can be done on reth ci side to avoid such issues in the future. (i.e. adding some ci step that ensures that the current version is actually installable as cargo dependency).

[mattsse]

I think this can be solved by manually updating the lockfile cargo update -p smallvec

but I think we can also do this

wdyt @DaniPopes

[DaniPopes]

Sure. In general if you have these sorts of problems it's good to first check cargo update, or in extreme cases deleting Cargo.lock entirely