fix: Add user agent for Braket interactions

[kshitijc]

Issue #, if available:

Description of changes:

Testing done:

• Validated that the user agent is being populated correctly.

Merge Checklist

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General

• [x] I have read the CONTRIBUTING doc
• [x] I used the commit message format described in CONTRIBUTING
• [x] I have updated any necessary documentation, including READMEs and API docs (if appropriate)

Tests

• [x] I have added tests that prove my fix is effective or that my feature works (if appropriate)
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[codecov[bot]]

Codecov Report

Merging #70 (b50bfe5) into main (6d8cdf9) will not change coverage. The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main       #70   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            6         6           
  Lines          207       210    +3     
  Branches        36        36           
=========================================
+ Hits           207       210    +3     

Impacted Files	Coverage Δ
src/braket/ocean_plugin/braket_sampler.py	100.00% <100.00%> (ø)

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