Fix init help message.

[rumpl]

- What I did

Docker App doesn't take a docker-compose file implicitly any more.

- How I did it

Removed the incorrect statement in the help.

- How to verify it

Run docker app init --help.

[silvin-lubecki]

LGTM

[codecov]

Codecov Report

Merging #689 into master will decrease coverage by 0.04%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #689      +/-   ##
==========================================
- Coverage   71.82%   71.77%   -0.05%     
==========================================
  Files          56       56              
  Lines        2889     2888       -1     
==========================================
- Hits         2075     2073       -2     
- Misses        550      551       +1     
  Partials      264      264

Impacted Files	Coverage Δ
internal/commands/init.go	86.66% <100%> (ø)	⬆️
types/parameters/parameters.go	92.06% <0%> (-1.59%)	⬇️
internal/commands/cnab.go	71.24% <0%> (-0.13%)	⬇️

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