Fix pk sequence value update negative 2

[timb07]

The branch in #51 was merged into a different branch instead of into main. This PR has the same changes.

[github-actions]

Coverage Report Results

Name	Stmts	Miss	Branch	BrPart	Cover
src/psycopack/__init__.py	6	0	0	0	100%
src/psycopack/_commands.py	116	0	6	0	100%
src/psycopack/_conn.py	5	0	0	0	100%
src/psycopack/_const.py	3	0	0	0	100%
src/psycopack/_cur.py	24	0	2	0	100%
src/psycopack/_identifiers.py	12	0	2	0	100%
src/psycopack/_introspect.py	174	0	16	0	100%
src/psycopack/_logging.py	2	0	0	0	100%
src/psycopack/_psycopg.py	5	0	0	0	100%
src/psycopack/_registry.py	58	0	6	0	100%
src/psycopack/_repack.py	364	0	124	0	100%
src/psycopack/_tracker.py	165	0	36	0	100%
tests/conftest.py	19	0	0	0	100%
tests/factories.py	41	0	10	0	100%
tests/test_cur.py	20	0	2	0	100%
tests/test_fixtures.py	5	0	0	0	100%
tests/test_package.py	3	0	0	0	100%
tests/test_repack.py	786	0	10	0	100%
TOTAL	1808	0	214	0	100%

1 empty file skipped.