chore: remove crowdloan pallet

[weichweich]

No Ticket

• remove and clean the Crowdloan Contributor pallet (it served it's purpose)
• pay the dust to the treasury

Checklist:

• I have verified that the code works
  • No panics! (checked arithmetic ops, no indexing array[3] use get(3), ...)
• I have verified that the code is easy to understand
  • If not, I have left a well-balanced amount of inline comments
• This PR does not introduce new custom types
  • If not, I have opened a companion PR with the type changes in the KILT types-definitions repository
• I have left the code in a better state
• I have documented the changes (where applicable)

[ntn-x2]

LGTM! I am just unsure whether it is best to change the pallet and runtime versions inside a PR like this. I would rather change them at the beginning or end of the development cycle with a separate PR.

[weichweich]

LGTM! I am just unsure whether it is best to change the pallet and runtime versions inside a PR like this. I would rather change them at the beginning or end of the development cycle with a separate PR.

yes. i reverted the version upgrade

[ntn-x2]

I also updated the PR description 👌

[wischli]

LGTM