[action] [PR:18610] [configlet] Skip last_update_time for comparison per design (sonic-net#997)

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### Description of PR
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Summary: Skip last_update_time per design.
Fixes # (issue) ADO: 32970571

### Type of change

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- Fill x for your type of change.
- e.g.
- [x] Bug fix
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- [ ] Bug fix
- [ ] Testbed and Framework(new/improvement)
- [ ] New Test case
 - [ ] Skipped for non-supported platforms
- [ ] Test case improvement

### Back port request
- [ ] 202205
- [ ] 202305
- [ ] 202311
- [ ] 202405
- [ ] 202411
- [ ] 202505

### Approach
#### What is the motivation for this PR?
Due to recent change in sonic-net/sonic-platform-daemons#604, the last_udpate_time was added. It should be skipped for comparison per design.
The `last_update_time` field was added in four place including `post_diagnostic_values_to_db, post_port_dom_flags_to_db, post_port_transceiver_hw_status_flags_to_db, post_port_vdm_thresholds_to_db`.
So there are many table involved such as `TRANSCEIVER_STATUS`, `TRANSCEIVER_STATUS_FLAG`. Thus skip in the val comparison.
#### How did you do it?
Skip the last_update_time for comparison
#### How did you verify/test it?
E2E
#### Any platform specific information?

#### Supported testbed topology if it's a new test case?

### Documentation
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Author: mssonicbld

tests/common/configlet/utils.py

@@ -135,7 +135,9 @@ def do_pause(secs, msg):
                 "TRANSCEIVER_STATUS",
                 "TRANSCEIVER_STATUS_FLAG_CLEAR_TIME\\|Ethernet[0-9]+"
             },
-            "keys_skip_val_comp": set()
+            "keys_skip_val_comp": {
+                "last_update_time"
+            }
         }
     }