Fix clippy errors

[sile]

Copilot Summary

This pull request includes changes to the SpanHandle implementation in the src/span.rs file. The changes are primarily focused on simplifying the code by removing unnecessary references in the context, start_child_span, and start_follows_from_span methods.

Here are the key changes:

• src/span.rs: In the SpanHandle implementation, the context method was updated to remove the unnecessary reference in the map function. This simplifies the code and makes it more readable.
• src/span.rs: In the SpanHandle implementation, the start_child_span method was updated to remove the unnecessary references in the if let statement. This change simplifies the code and improves readability.
• src/span.rs: Similarly, in the SpanHandle implementation, the start_follows_from_span method was updated to remove the unnecessary references in the if let statement. This change also simplifies the code and improves readability.