text: Title: Validate function signature
  Body: `_validate_and_modify_signature` takes a function as an argument to validate and modify its signature. we need to check that no arguments (other than the first one) start with `env`:
  
  Example:
  
  ```python
  # good: a, b do not start with env
  def works(env, a, b):
      pass
  ```
  
  ```python
  # bad: env_something starts with env
  def does_not_work(env, a, env_something):
      pass
  ```
  
  https://github.com/ploomber/ploomber/blob/2e0d764c8f914ba21480b275c545ea50ff800513/src/ploomber/env/decorators.py#L15
  
  Please create a new file named `test_decorators.py` here: https://github.com/ploomber/ploomber/tree/master/tests/env and add a few tests
  