Change default value of Method RequestParameters from true to false

[josh-feather]

Changes made in the 1.10.3 release made cache-key parameters required by default, changing the behaviour from 1.10.2 and introducing a breaking change.

This PR addresses the last comment by @DianaIonita in #134 suggesting we go back to making cache-key parameters optional by default, whilst still being able to make them required via events.http.request.parameters:

Hi everyone,

This is my suggestion:

set the default of not required on cache key parameters
if anyone wants to require cache key parametres, they can do it via the already existing serverless framework config (events.http.request.parameters)
This way, we avoid the confusion of having two config options that do the same thing. It also doesn't need the developer to remember any special behaviours of this caching plugin.

Fixes #133

[DianaIonita]

Much appreciated @josh-feather!