Remove redundant envfile

[ulyssessouza]

Closes #495

- What I did
Remove redundant envfile section on render

- How I did it
By passing the option to remove it after resolving the envvars

- How to verify it
Please refer to #495 (comment) for the steps to reproduce

- Description for the changelog
Remove redundant envfile section on render

- A picture of a cute animal (not mandatory but encouraged)

[silvin-lubecki]

LGTM

[ndeloof]

LGTM
still feeling uncomfortable that we rely on random commit just like things will never change after a PR has been merged

[silvin-lubecki]

@ndeloof I know we rely on the docker/cli master branch, but we need to move on this. Moreover there will be a docker/cli release soon, and we will bump the cli then before next docker/app release 👍

[rumpl]

LGTM ready to merge when green

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@856c60a). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master     #634   +/-   ##
=========================================
  Coverage          ?   71.95%           
=========================================
  Files             ?       49           
  Lines             ?     2560           
  Branches          ?        0           
=========================================
  Hits              ?     1842           
  Misses            ?      486           
  Partials          ?      232

Impacted Files	Coverage Δ
render/render.go	80.23% <100%> (ø)

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