Lower PII annotation threshold so that I can enable enforcement

The CMS check is currently reporting 94.5% coverage, so I must lower to
that value or else quality checks will fail on master after I merge.

DE-1764

.pii_annotations.yml

 source_path: ./
 report_path: pii_report
 safelist_path: .annotation_safe_list.yml
-coverage_target: 100.0
+coverage_target: 94.5
 # See OEP-30 for more information on these values and what they mean:
 # https://open-edx-proposals.readthedocs.io/en/latest/oep-0030-arch-pii-markup-and-auditing.html#docstring-annotations
 annotations: