work around for "self" based input bindings for optional inputs

[mr-c]

see common-workflow-language/common-workflow-language#559 (comment)

[swzCuroverse]

@mr-c I believe this is done. https://www.commonwl.org/user_guide/faq.html#setting-self-based-input-bindings-for-optional-inputs
If so, can you close this ticket?

Thanks for pointing this out, @Fienne

[mr-c]

As per common-workflow-language/common-workflow-language#559 (comment) that bug in cwltool was fixed in 2018, so https://www.commonwl.org/user_guide/faq.html#setting-self-based-input-bindings-for-optional-inputs should be removed from the FAQ (and we should check to see if we were using this workaround anywhere in the user guide, and remove it)