ci: cram: reboot TimeStamp precision

Problem:
reboot TimeStamp precision has changed: unnecessary fraction of seconds have been removed
This simplification change has been introduced in PPW-1605 in the reboot-service when
the reboot timestamp is now set to unknow when the HGW isn't NTP synced.

Solution:
change the cram test timestamp check

Reference: PPW-1605
Signed-off-by: Florian Rouzaud <florian.rouzaud@softathome.com>

.gitlab/tests/cram/generic/acceleration-plan-components/095-reboot-service.t

@@ -21,7 +21,7 @@ Check the root datamodel settings:
       "Cause": "LocalFactoryReset",
       "FirmwareUpdated": 0,
       "Reason": "Power lost",
-      "TimeStamp": "\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}.\d+Z" (re)
+      "TimeStamp": "\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(?:\.\d+)?Z" (re)
     }
   }