adding quotes for zsh shell issue

[TuanaCelik]

Proposed changes:

• Adding quotes around square brackets in install commands to go around the zsh shell issue. Works for others as well
  @ZanSara, I'll also add quotes to the line in import_utils.py below:

def _optional_component_not_installed(component: str, dep_group: str, source_error: Exception):
    raise ImportError(
        f"Failed to import '{component}', "
        "which is an optional component in Haystack.\n"
        f"Run 'pip install farm-haystack[{dep_group}]' "
        "to install the required dependencies and make this component available."
    ) from source_error

What this prompt suggests will also result in zsh: no matches found: farm-haystack[crawler].
But let me know if I should keep them out here.

Status (please check what you already did):

• [ x] First draft (up for discussions & feedback)
• Final code
• Added tests
• Updated documentation