feat: update tbDEXHttpClient to use submitCancel()

[ethan-tbd]

this pr replaces the submitClose() method with submitCancel() since the Close message is reserved for PFI use while the Cancel message is reserved for clients

[github-actions]

TBD Spec Test Vectors Report

Total Test Vectors	Total Test Cases	✅ Passed	❌ Failed	⚠️ Skipped
10	10	10	0	0

✅ All test vectors passed

---

Automatically generated at: 2024-08-28T18:24:52.019Z

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.

Project coverage is 93.59%. Comparing base (7d7e6d5) to head (2869b5b).

Files with missing lines	Patch %	Lines
...s/tbDEXTests/HttpClient/tbDEXHttpClientTests.swift	83.33%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #104   +/-   ##
=======================================
  Coverage   93.59%   93.59%           
=======================================
  Files          36       36           
  Lines        1374     1374           
=======================================
  Hits         1286     1286           
  Misses         88       88           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.