fix: Correct Markdown format for Tracing link in README

[noid11]

Issue #, if available: fix markdown link format

Description of changes: fix Trancing link format

 ## Tracing and Logging

-The Rust Runtime for Lambda integrates with the (Tracing)[https://tracing.rs] libraries to provide tracing and logging.
+The Rust Runtime for Lambda integrates with the [Tracing](https://tracing.rs) libraries to provide tracing and logging.

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• [x] I confirm that my contribution is made under the terms of the Apache 2.0 license.
• [x] I confirm that I've made a best effort attempt to update all relevant documentation.