fix: correct a typo in the help message for the powershell autocompletion

[suzuki-shunsuke]

What type of PR is this?

• bug

What this PR does / why we need it:

Correct a typo in the help message.

• Output the script to path/to/autocomplete/aqua.ps1 an run it. aquaproj/aqua#4972

$ aqua completion --help
NAME:
   aqua completion - Output shell completion script for bash, zsh, fish, or Powershell

USAGE:
   aqua completion [command [command options]]

DESCRIPTION:
   Output shell completion script for bash, zsh, fish, or Powershell.
   Source the output to enable completion.

   # .bashrc
   source <(aqua completion bash)

   # .zshrc
   source <(aqua completion zsh)

   # fish
   aqua completion fish > ~/.config/fish/completions/aqua.fish

   # Powershell
   Output the script to path/to/autocomplete/aqua.ps1 an run it.

Output the script to path/to/autocomplete/aqua.ps1 an run it.

an in an run it. is a typo of and.

Which issue(s) this PR fixes:

(REQUIRED)

Special notes for your reviewer:

(fill-in or delete this section)

Testing

(fill-in or delete this section)

Release Notes

(REQUIRED)

Correct a typo in the help message