chore: remove unnecessary asserts

[glevco]

Depends on #967

Motivation

Since the BaseTransaction.hash property has been converted from Optional[bytes] to bytes, multiple assertions can be removed.

Acceptance Criteria

• Remove instances of assert tx.hash is not None and equivalent.

Checklist

• If you are requesting a merge into master, confirm this code is production-ready and can be included in future releases as soon as it gets merged

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.08%. Comparing base (adc0191) to head (20f5c6d).
Report is 2 commits behind head on master.

❗ Current head 20f5c6d differs from pull request most recent head 04a8ed9. Consider uploading reports for the commit 04a8ed9 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #968      +/-   ##
==========================================
- Coverage   85.10%   85.08%   -0.03%     
==========================================
  Files         296      295       -1     
  Lines       22909    22755     -154     
  Branches     3449     3443       -6     
==========================================
- Hits        19497    19360     -137     
+ Misses       2732     2710      -22     
- Partials      680      685       +5     

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