Expression tests: std_normal_log_qf requires non-positive argument

[WardBrian]

Follow on to #2824, the new function from #2744 requires an argument <=0.

I have run the expression tests for this locally and confirmed they passed after this change, so this will unblock stan-dev/stanc3#1258

Checklist

• Math issue #(issue number)

• Copyright holder: Simons Foundation

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  - Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
  - Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

• the basic tests are passing

  • unit tests pass (to run, use: ./runTests.py test/unit)
  • header checks pass, (make test-headers)
  • dependencies checks pass, (make test-math-dependencies)
  • docs build, (make doxygen)
  • code passes the built in C++ standards checks (make cpplint)

• the code is written in idiomatic C++ and changes are documented in the doxygen

• the new changes are tested