tests: Avoid overflowing signed 32 bit time_t.
* tests/openpgp/quick-key-manipulation.scm: Use expiration times in the year 2038 instead of 2105 to avoid overflowing 32 bit time_t. time_t is used internally to parse the expiraton time from the iso timestamp.
- GnuPG-bug-id: T2988
- Signed-off-by: Justus Winter <justus@g10code.com>