[Chapel Merge] Fix another error with GCC 5.4

Branch: refs/heads/main
Revision: f6f16f6
Author: mppf
Log Message:

Merge pull request #18161 from mppf/fix-gcc-54-error

Fix another error with GCC 5.4

Follow-up to #18122.

See also #18133 and 60970 – Support std::hash with enum types (LWG 2148)

Trivial and not reviewed.

Modified Files:
M compiler/next/include/chpl/resolution/resolution-types.h

Compare: https://github.com/chapel-lang/chapel/compare/0f62b7c40b69...f6f16f6bd78f