Auto merge of #4282 - bundler:seg-travis-remove-frozen-string, r=segiddins
Auto merge of #4282 - bundler:seg-travis-remove-frozen-string, r=segiddins

[Travis] Remove special frozen string literal build

That build entry is redundant  -- we test frozen string literals in all of the 2.3.0 builds now.

seanlinsley/bundler,bronzdoc/bundler,bundler/bundler,asutoshpalai/bundler,bronzdoc/bundler,RochesterinNYC/bundler,asutoshpalai/bundler,bundler/bundler,mvz/bundler,dilumnavanjana/bundler,dilumnavanjana/bundler,mvz/bundler,RochesterinNYC/bundler,seanlinsley/bundler