fix(wallet): build with no default features

[ValuedMammal]

Candidate for fixing an issue preventing bdk_wallet to build with no default features.

Something to do with #1625 changed the way bdk_wallet resolves its dependency on rust-miniscript. Running cargo build -p bdk_wallet --no-default-features from the workspace root returns

error: at least one of the std or no-std features must be enabled

I started by adding the "no-std" feature to the miniscript dependency in Cargo.toml which caused compilation to fail again because Condition is not Ord so I added that here but there might be an alternative solution I haven't thought of.

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran cargo fmt and cargo clippy before committing

New Features:

• I've added tests for the new feature
• I've added docs for the new feature

Bugfixes:

• This pull request breaks the existing API
• I've added tests to reproduce the issue which are now passing
• I'm linking the issue being fixed by this PR