Remove gcc-9 as expected failure from broken_constant_eval.pass.cpp

[wmaxey]

gcc-9/10 non-constant pass/fail

• pass - gcc-8.4.0
• pass - gcc-8.4.1
• untested - gcc-9.0.0
• pass - gcc-9.1.0
• pass - gcc-9.3.1
• pass - gcc-10.0.0
• fail - gcc-10.1.0
• fail - gcc-10.2.0

This broke tests covering gcc-9, and will break tests with gcc-10.0.
This seems consistent with different versions of NVCC.

#21 is root cause.