build: remove @zilliqa-js/contract dep in @zilliqa-js/blockchain

[ghost]

Description

This PR removes unnecessary @zilliqa-js/contract in @zilliqa-js/blockchain package.json.
When it is not removed, it creates circular dependency since #379

Motivation and Context

How has this been tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• Add tests to cover changes as needed.
• Update documentation as needed.

[codecov-commenter]

Codecov Report

Merging #410 (32a3cf6) into dev (67115d0) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##              dev     #410   +/-   ##
=======================================
  Coverage   82.16%   82.16%           
=======================================
  Files          43       43           
  Lines        1811     1811           
  Branches      331      331           
=======================================
  Hits         1488     1488           
  Misses        322      322           
  Partials        1        1           

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[ghost]

rebase