make package compatible with guzzle7

[davidverholen]

current spryker release uses Guzzle 7 which does not work with this module anymore

• changed dependency to guzzle7-adapter
• changed use statement in sdk factory to use guzzle 7 adapter

[lars85]

we would love to see the guzzle7 adapater in the master branch

[txboezkanyilmaz]

Thanks for your effort. Hopefully it will be merged soon.

[abitskil]

Dear @davidverholen,

We want to express our appreciation for your recent contribution to our project.

Your pull request has been diligently reviewed, processed following our internal processes, and successfully merged into our codebase. It is now part of the release, which you can find under the 2.1.0.

Thanks a lot for your contribution!

Best,
Spryker Team