Fix chplconfig test after improved chplenv error checking

[jabraham17]

Fixes a failing test (test/chplenv/chplconfig/warnings/warnings.chpl) resulting from #26501.

This issue occurs in a very strange way.

1. The test system always explicitly sets CHPL_GASNET_SEGMENT, in the default shared mem config this will always be none
os.environ["CHPL_GASNET_SEGMENT"] = chpl_comm_segment.get()
2. This test uses a value of CHPL_COMM=gasnet when testing for multiple values of CHPL_COMM in a chplconfig file.
3. This test uses a custom script to ensure a clean environment when diff-ing the test output, test/chplenv/chplconfig/unset_overrides.sh.
   • This script uses the --overrides flag of printchplenv to determine what variables to unset.
4. By default, --tidy is thrown by printchplenv to restrict the chplenv output to only relevant variables, e.g. with CHPL_COMM=none, gasnet specific variables aren't shown

This results in the good file for the test being generated with CHPL_COMM=gasnet and CHPL_GASNET_SEGMENT=none, which is not valid. This is allowed to happen because the unset_overrides.sh script is unintentionally leaving garbage chplenv variables behind.

The solution to this is to make unset_overrides.sh explicitly use --no-tidy, so that it actually does what it is supposed to. Note this must be done before --overrides on the CLI, otherwise it has no effect (flags are applied in order)

This PR also fixes a typo I noticed while determining all this.

[Reviewed by @lydia-duncan]

[lydia-duncan]

This looks good, assuming you also ran test/chplenv/chplconfig/correctness/, which looks like it relies on this file

[jabraham17]

Yup! I ran start_test test/chplenv