Removed $ from the commands in Readme

[AbhishekDoshi26]

What does this change?

Earlier the readme had $ in the commands, for example $ brew install FlutterGen/tap/fluttergen so when we copy the command from pub.dev, it comes with the $ sign which doesn't work on terminal.

This PR removes the $ from the commands.

Fixes #<issue_number_goes_here> 🎯

Type of change

Please delete options that are not relevant.

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

Checklist:

Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

• Make sure to open a GitHub issue as a bug/feature request before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
  • Ensure the tests (melos run unit:test)
  • Ensure the analyzer and formatter pass (melos run format to automatically apply formatting)
• Appropriate docs were updated (if necessary)