Update the group name for the UmaAndUkmDemographics test

Change-Id: I87319ac1548bde596dedeb65fa8f02c762590734
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2032229Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#737435}

testing/variations/fieldtrial_testing_config.json

@@ -6838,7 +6838,7 @@
             ],
             "experiments": [
                 {
-                    "name": "UMA_Enabled",
+                    "name": "UMA_Enabled_202002",
                     "enable_features": [
                         "DemographicMetricsReporting"
                     ],