[MOB-9346] Use flutter pub get instead of pub get

[DavidMina96]

Description of the change

• Use flutter pub get command instead of the outdated pub get (fixes this error)

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Related issues

Issue links go here

Checklists

Development

• Lint rules pass locally
• The code changed/added as part of this pull request has been covered with tests

Code review

• This pull request has a descriptive title and information useful to a reviewer
• Issue from task tracker has a link to this pull request