Documentation suggests removed --install-scripts flag

[ndevenish]

The documentation for --install-options (online at https://pip.pypa.io/en/latest/cli/pip_install/#cmdoption-install-option) gives the example of passing --install-scripts. Since #7309 this is now an invalid option. This example should be updated (and perhaps the current way to achieve this added).

Text comes from: https://github.com/pypa/pip/blob/87aee20df2890a89f70eecbd7086262146a2e64a/src/pip/_internal/cli/cmdoptions.py#L799-L810

A comment on the deprecation issue asked for this to be opened at: https://github.com/pypa/pip/issues/7309#issuecomment-676581862

[hsadia538]

@ndevenish I want to work on this.

[Patelrahul4884]

@ndevenish I can work on this issue

[Patelrahul4884]

@ndevenish do we have to completely remove install_options variable?