Disable eth-gas-reporter when present in truffle config

[cgewecke]

#423

It hangs & its gas data is meaningless here.

[codecov-io]

Codecov Report

Merging #448 into buidler-plugin will increase coverage by <.01%.
The diff coverage is 100%.

@@                Coverage Diff                 @@
##           buidler-plugin     #448      +/-   ##
==================================================
+ Coverage           99.22%   99.22%   +<.01%     
==================================================
  Files                  20       20              
  Lines                 773      776       +3     
==================================================
+ Hits                  767      770       +3     
  Misses                  6        6

Impacted Files	Coverage Δ
plugins/resources/truffle.utils.js	100% <100%> (ø)	⬆️

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