Revert "Update filecoin-cxx deps, mainly multihash"

[cdesouza-chromium]

This reverts commit a1db616.

After merge, we started getting some issues in the CI relating to license files:

 FAILED: gen/components/resources/about_credits.html 
17:28:32  python3 ../../tools/licenses/licenses.py --target-os=linux --depfile gen/components/resources/about_credits.d credits gen/components/resources/about_credits.html
17:28:32  Traceback (most recent call last):
17:28:32    File "/home/ubuntu/workspace/brave-browser-build-linux-x64-nightly/src/out/Release/../../tools/licenses/licenses.py", line 1451, in <module>
17:28:32      sys.exit(main())
17:28:32               ^^^^^^
17:28:32    File "/home/ubuntu/workspace/brave-browser-build-linux-x64-nightly/src/out/Release/../../tools/licenses/licenses.py", line 1434, in main
17:28:32      if not GenerateCredits(
17:28:32             ^^^^^^^^^^^^^^^^
17:28:32    File "/home/ubuntu/workspace/brave-browser-build-linux-x64-nightly/src/out/Release/../../tools/licenses/licenses.py", line 1039, in GenerateCredits
17:28:32      ReportBraveIncompleteMetadataFile(path)
17:28:32    File "/home/ubuntu/workspace/brave-browser-build-linux-x64-nightly/src/brave/script/brave_license_helper.py", line 353, in ReportBraveIncompleteMetadataFile
17:28:32      raise ValueError(
17:28:32 

Resolves

Submitter Checklist:

• I confirm that no security/privacy review is needed and no other type of reviews are needed, or that I have requested them
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Squashed any review feedback or "fixup" commits before merge, so that history is a record of what happened in the repo, not your PR
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally:
  • npm run test -- brave_browser_tests, npm run test -- brave_unit_tests wiki
  • npm run presubmit wiki, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on
• All relevant documentation has been updated, for instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protections
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan: