Change captured site test to use generic --force-fieldtrials param

We need behavior triggered by the presence of a "--force-fieldtrials"
but we also want to remove the deprecated flag connected to
AutofillFieldMetadata.

Putting in a stub to unblock that deprecation work while keeping the
tests up and running.

Bug: 1151207
Change-Id: I790cef05abd7d8a436627a438d665bffaa8158d8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2552281
Auto-Submit: Ian Struiksma <ianstruiksma@google.com>
Reviewed-by: Christoph Schwering <schwering@google.com>
Commit-Queue: Christoph Schwering <schwering@google.com>
Cr-Commit-Position: refs/heads/master@{#829622}

chrome/browser/autofill/autofill_captured_sites_interactive_uitest.cc

@@ -238,8 +238,7 @@ class AutofillCapturedSitesInteractiveTest
         /*enabled_features=*/{features::kAutofillShowTypePredictions},
         /*disabled_features=*/{features::kAutofillCacheQueryResponses});
     command_line->AppendSwitch(switches::kShowAutofillTypePredictions);
-    command_line->AppendSwitchASCII(::switches::kForceFieldTrials,
-                                    "AutofillFieldMetadata/Enabled/");
+    command_line->AppendSwitchASCII(::switches::kForceFieldTrials, "Foo/Bar");
 
     captured_sites_test_utils::TestRecipeReplayer::SetUpCommandLine(
         command_line);