Revert `SendXcmOrigin` in Rococo & Westend (#2571)

Based on issue
[#2512](https://github.com/paritytech/polkadot-sdk/issues/2512

), it
seems that some ecosystem teams are using these networks to set up their
staging environments and test certain use cases, some of them involving
sending XCMs from the relay with origins not allowed in the current
configuration.

This change reverts the configuration of `SendXcmOrigin`.

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Co-authored-by: Adrian Catangiu <[email protected]>