Fix Bool then-load return value docs

[fallintoplace]

Summary

• Fix Bool logical*ThenLoad docs to say they return the resulting value, not the original value.
• Update the .gyb source and regenerate Sources/Atomics/Conformances/autogenerated/AtomicBool.swift.

Why

logicalAndThenLoad, logicalOrThenLoad, and logicalXorThenLoad compute the new value after applying the logical operation and return that value. The existing docs described the return value as the original value, which matches loadThenLogical* but not the *ThenLoad APIs.

Notes

This is documentation-only; the implementations already return the resulting value.