Fix use of deprecated Buffer constructor

[DarcyRaynerDD]

What does this PR do?

Replaces deprecated buffer constructor use with Buffer.from method

Motivation

Issue #168

Testing Guidelines

Additional Notes

Types of Changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
• This PR's changes are covered by the automated tests
• This PR collects user input/sensitive content into Datadog
• This PR passes the integration tests (ask a Datadog member to run the tests)

[codecov-io]

Codecov Report

Merging #169 (0635ad5) into main (5d1d7e0) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #169   +/-   ##
=======================================
  Coverage   86.53%   86.53%           
=======================================
  Files          31       31           
  Lines        1203     1203           
  Branches      236      236           
=======================================
  Hits         1041     1041           
  Misses        106      106           
  Partials       56       56           

Impacted Files	Coverage Δ
src/trace/context.ts	90.51% <100.00%> (ø)

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