Update the download emulators default to true.

[christhompsongoogle]

Update the download emulators default to true. The user has indicated that they want to use the emulators we should download them right away to speed up their use and enable the suite to work better offline.

[codecov-commenter]

Codecov Report

Base: 56.27% // Head: 56.27% // No change to project coverage :thumbsup:

Coverage data is based on head (9f7372d) compared to base (e984a6c). Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5123   +/-   ##
=======================================
  Coverage   56.27%   56.27%           
=======================================
  Files         309      309           
  Lines       20820    20820           
  Branches     4224     4224           
=======================================
  Hits        11716    11716           
  Misses       8092     8092           
  Partials     1012     1012           

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