Simplify some conditionals in circuit_get_open_circ_or_launch()

When entry_list_is_constrained() is true, guards_retry_optimistic()
always returns true.

When entry_list_is_constrained() is false,
options->UseBridges is always false,
therefore !options->UseBridges is always true,
therefore (!options->UseBridges || ...) is always true.

Cleanup after #24367.