Update feature_category to :fuzz_testing for fuzzing specs
Update the feature_category metadata in the following spec files to :fuzz_testing:
- ee/spec/finders/app_sec/fuzzing/coverage/corpuses_finder_spec.rb
- ee/spec/graphql/mutations/app_sec/fuzzing/coverage/corpus/create_spec.rb
- ee/spec/graphql/resolvers/app_sec/fuzzing/coverage/corpuses_resolver_spec.rb
- ee/spec/graphql/types/app_sec/fuzzing/api/ci_configuration_type_spec.rb
- ee/spec/graphql/types/app_sec/fuzzing/api/scan_mode_enum_spec.rb
- ee/spec/graphql/types/app_sec/fuzzing/api/scan_profile_type_spec.rb
- ee/spec/graphql/types/app_sec/fuzzing/coverage/corpus_type_spec.rb
- ee/spec/graphql/types/vulnerability_location/coverage_fuzzing_type_spec.rb
This aligns the specs with the fuzz_testing feature category for fuzzing-related functionality.