docs: remove duplicate documentation directory (#1159)

In #1142 ("Updates to upstream to sync with downstream content"),
`docs/userguide/modules/creating-service-bindings` was moved to
`docs/userguide/modules/binding-workloads-using-sbo`, and its content
was changed to reflect documentation changes downstream.  However, this
first directory was kept around, leaving stale documentation in our
repository.  This change removes this directory and its stale
documentation to prevent further confusion.

Signed-off-by: Andy Sadler <[email protected]>

Author: sadlerap