docs(pfm): ordering matters in the transferStack (porttypes.IBCModule)

[Reecepbcups]

reference: https://github.com/CosmosContracts/juno/pull/1044

Ensure to keep PFM higher in the stack compared to other middlewares / modules. This way custom implementation such as ICS29 do not break due to custom handler methods PFM does not support (and never will or should)

Found by: Luca @ informal