Remove redundant code in usage function

[DannyBen]

Before this PR, when command summary and help were the same (single line help), the generated code looked like this:

# :command.usage
rush_usage() {
  if [[ -n $long_usage ]]; then
    printf "rush - Personal package manager.\n"
    echo

  else
    printf "rush - Personal package manager.\n"
    echo

  fi

This PR fixes that

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Note that the other changed files in the PR (approvals mostly) are due to updates in completely.