Fix london gas bug / bump deps

[cgewecke]

• ganache-cli to 6.12.2
• solidity-parser/parser to 0.13.2

We need to keep gasPrice for backwards compat - use suggestion in issue 652

networkConfig.initialBaseFeePerGas = 0;

[codecov-commenter]

Codecov Report

Merging #658 (73c45c9) into master (b162bef) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #658   +/-   ##
=======================================
  Coverage   98.68%   98.68%           
=======================================
  Files          22       22           
  Lines         986      987    +1     
=======================================
+ Hits          973      974    +1     
  Misses         13       13           

Impacted Files	Coverage Δ
plugins/resources/nomiclabs.utils.js	100.00% <100.00%> (ø)

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