Testing: pyupgrade, remove unnecessary import from future; rucio#6538

See also:
- https://docs.astral.sh/ruff/rules/unnecessary-future-import/

lib/rucio/common/cache.py

@@ -11,7 +11,6 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-from __future__ import absolute_import
 
 from typing import TYPE_CHECKING