Remove stale BitcoinDevKitTests target from Package.swift

[ANAMASGARD]

Fixes bitcoindevkit/bdk-ffi#912

What this does

Removes the stale .testTarget(name: "BitcoinDevKitTests") entry from Package.swift.

Why

The Tests/ folder was removed from bdk-swift, but Package.swift still declared a test target pointing to it. This mismatch makes a fresh clone fail with:

error: Source files for target BitcoinDevKitTests should be located under 'Tests/BitcoinDevKitTests', ...

Now the manifest matches what's actually in the repo, so a fresh clone resolves and builds cleanly.

Scope

• Only Package.swift changed (3 lines removed).
• No changes to bdk-ffi/bdk-swift (not needed, per the issue).

Verification

• swift package describe succeeds (no missing test-target error).
• swift build / swift test no longer fail on the stale test target path.

Fixes bitcoindevkit/bdk-ffi#912
Ref: bitcoindevkit/bdk-ffi#912

[reez]

Thanks, this looks good to me. I verified that the standalone bdk-swift dist repo no longer has Tests/BitcoinDevKitTests, so removing the stale .testTarget(name: "BitcoinDevKitTests") entry from this repo’s Package.swift is the right fix.

Before merging this, I think I might want to make a companion source-of-truth update in bdk-ffi: remove the same stale test target from bdk-swift/Package.swift.txt, since the publish-spm workflow uses that template to regenerate this repo’s Package.swift. That will prevent a future release from reintroducing this. I’ll leave this PR open until that companion update is handled.