Add -f shorthand to app rm --force

[zappy-shu]

- What I did

Makes -f the shorthand for --force in docker app rm, same as in docker rm and docker app image rm

- How I did it

Use BoolVarP for the force option

- How to verify it

Run docker app rm --help The output should show -f as an alias for --force like so:

Options:
      --credential stringArray       Add a single credential, additive ontop of any --credential-set used
      --credential-set stringArray   Use a YAML file containing a credential set or a credential set present in the credential store
  -f, --force                        Force the removal of a running App
      --with-registry-auth           Sends registry auth

- Description for the changelog

Add -f shorthand to app rm --force

- A picture of a cute animal (not mandatory)

[silvin-lubecki]

LGTM

[codecov]

Codecov Report

Merging #776 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #776   +/-   ##
=======================================
  Coverage   70.44%   70.44%           
=======================================
  Files          67       67           
  Lines        3729     3729           
=======================================
  Hits         2627     2627           
  Misses        758      758           
  Partials      344      344

Impacted Files	Coverage Δ
internal/commands/remove.go	50.94% <100%> (ø)	⬆️

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