[omnibox field trial] Update testing configuration list

Add/remove recent experiments from field trial experiment list.
Only updated desktop, per the Finch warning.

Bug: 726769
Change-Id: I5ad8b113d60b703f3c61e24f1dd17ae9b3d2a2b7
Reviewed-on: https://chromium-review.googlesource.com/c/1342758
Commit-Queue: Kevin Bailey <krb@chromium.org>
Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610840}

testing/variations/fieldtrial_testing_config.json

@@ -3243,13 +3243,11 @@
                         "UIVerticalMargin": "10"
                     },
                     "enable_features": [
-                        "OmniboxBreakWordsAtUnderscores",
                         "OmniboxDisplayTitleForCurrentUrl",
                         "OmniboxNewAnswerLayout",
                         "OmniboxRichEntitySuggestions",
                         "OmniboxTailSuggestions",
-                        "OmniboxUIExperimentHideSteadyStateUrlScheme",
-                        "OmniboxUIExperimentHideSteadyStateUrlTrivialSubdomains",
+                        "OmniboxUIExperimentMaxAutocompleteMatches",
                         "ZeroSuggestRedirectToChrome",
                         "ZeroSuggestSwapTitleAndUrl"
                     ]