doc: Remove sphinx warning bt_ots_init pattern

The bt_ots_init struct has been renamed to bt_ots_init_param in commit:

  cf0ff30b

That was previously triggering a warning in Sphinx, due to the same
name being used for a struct and function, and this pattern
was designed to silence it. We don't need the pattern any more as the
warning is gone.

Signed-off-by: Michael Jones <m.pricejones@gmail.com>