Update get_Natmort in SS_benchfore.tpl to happen with predators

[Rick-Methot-NOAA]

Concisely (20 words or less) describe the issue

get_NatMort() needs to be called if predators are used

Please Link issue(s)

none
resolves #[add issue number number], resolves #[optional second issue number if more than 1 issue addressed.]

What tests have been done? Upload any model input files created for testing in a zip file, if possible.

none

What tests/review still need to be done? Who can do it, and by when is it needed (ideally)?

no need, tests had already occurred in old stale branch

Has any new code been documented?

none
If not, please add documentation before submitting the Pull Request.

• I have documented any new code added (or no new code was added)

is there an input change for users to Stock Synthesis?

• Yes, there was an input change

If so, please provide an example of the new inputs needed.

[New example stock synthesis input goes here]

Check which is true. This PR requires:

• no further changes to r4ss
• no further changes to the manual
• no further changes to SSI (the SS3 GUI)
• no further changes to the stock synthesis change log (new features, bug reports)

Describe any changes in r4ss/SS3 manual/SSI that are needed (if not checked):

none

If changes are needed in the change log, please fill in the table here:

Action	Topics	Type
[fix, new, or revise]	[e.g., biology. Use issue label options.]	[input, output, and/or calc, or ALL]

Additional information (optional):

none

[Rick-Methot-NOAA]

bypassing review