feature/capgen: ccpp_error_message unit update

[climbfuji]

Update unit of ccpp_error_message from 1 to none.

For feature/capgen: Update unit of ccpp_error_message from 1 to none as described in #397. When these changes get merged back to main, the workaround in parse_checkers.py that is only in main, not in feature/capgen, must also be removed.

User interface changes?: No

Fixes : [Github issue #s] And brief description of each issue.

Testing:
test removed: none
unit tests:
I ran the following doctests without failures:

ccpp-framework-errmsg-unit-update-feature-capgen/scripts/parse_tools [gccgfortran-py3-hpc-stack-1.2.1]> python parse_checkers.py
ccpp-framework-errmsg-unit-update-feature-capgen/scripts/parse_tools [gccgfortran-py3-hpc-stack-1.2.1]> python parse_log.py
ccpp-framework-errmsg-unit-update-feature-capgen/scripts/parse_tools [gccgfortran-py3-hpc-stack-1.2.1]> python parse_object.py
ccpp-framework-errmsg-unit-update-feature-capgen/scripts/parse_tools [gccgfortran-py3-hpc-stack-1.2.1]> python parse_source.py
ccpp-framework-errmsg-unit-update-feature-capgen/scripts/parse_tools [gccgfortran-py3-hpc-stack-1.2.1]> python preprocess.py
ccpp-framework-errmsg-unit-update-feature-capgen/scripts/parse_tools [gccgfortran-py3-hpc-stack-1.2.1]> python xml_tools.py
ccpp-framework-errmsg-unit-update-feature-capgen/scripts/parse_tools [gccgfortran-py3-hpc-stack-1.2.1]> cd ..
ccpp-framework-errmsg-unit-update-feature-capgen/scripts [gccgfortran-py3-hpc-stack-1.2.1]> python metadata_table.py
ccpp-framework-errmsg-unit-update-feature-capgen/scripts [gccgfortran-py3-hpc-stack-1.2.1]> python metavar.py
ccpp-framework-errmsg-unit-update-feature-capgen/scripts [gccgfortran-py3-hpc-stack-1.2.1]> python constituents.py

system tests:
I ran run_tests.sh in directory tests, all tests passed.

manual testing:
I tried to test this with the UFS. After removing the workaround in parse_checkers.py, the code generator tripped over the errflg mismatch that I just mentioned in ESCOMP/ESMStandardNames#19. A test with the UFS can only happen after this PR is merged into feature/capgen, and a reverse PR that updates main from feature/capgen and fixes errflg is created.

[gold2718]

Thanks!