test: fix operator precedence in manifest v2 assertions (#3612)

Six assertions in test_write_manifest and test_write_manifest_list used
the form `assert x == a if format_version == 1 else b`. Because a
conditional expression binds looser than `==`, Python parses this as
`assert (x == a) if (format_version == 1) else b`, so for the
format_version == 2 parametrization the whole statement collapses to
`assert b`, where b is a truthy constant (3, or ManifestContent.DELETES).
The v2 branch therefore always passed and never compared the actual
value read back from the manifest.

Wrap the right-hand side in parentheses so the conditional expression is
the comparison target. This restores verification of the v2
sequence_number, content, min_sequence_number, and file_sequence_number
on the manifest read/round-trip path. Test-only change; all parametrized
cases (v1 and v2) pass.

Signed-off-by: Anas Khan <83116240+anxkhn@users.noreply.github.com>