[Chapel Merge] Remove the word "possible" from these filtered err

Branch: refs/heads/master
Revision: 3d9f4c8
Author: lydia-duncan
Log Message:

Merge pull request #16364 from lydia-duncan/removePossibly

Remove the word “possible” from these filtered error messages
[reviewed by @ronawho]

We’re pretty certain that’s what’s going on when these trigger, so no need to
hedge on them.

Modified Files:
M util/test/sub_test

Compare: https://github.com/chapel-lang/chapel/compare/85ebfb3f3ae4...3d9f4c8f0712