Fix field trial experiment name; update field trial doc.

Change-Id: Ia05d04a3fcc5b4f24ecda9354835fb625ac6cdfe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1962995
Commit-Queue: Mark Pearson <mpearson@chromium.org>
Auto-Submit: Carlos Knippschild <carlosk@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#724090}

testing/variations/README.md

@@ -38,14 +38,14 @@ perf bots and browser tests in the waterfall.
 ```
 
 The config file is a dictionary at the top level mapping a study name to an
-array of *study configurations*. The study name in the configuration file should
-match the FieldTrial name used in the Chromium client code.
+array of *study configurations*. The study name in the configuration file
+**must** match the FieldTrial name used in the Chromium client code.
 
 > Note: Many newer studies do not use study names in the client code at all, and
 > rely on the [Feature List API][FeatureListAPI] instead. Nonetheless, if a
-> study has a server-side configuration, the study `name` specified here should
-> match the name specified in the server-side configuration; this is used to
-> implement sanity-checks on the server.
+> study has a server-side configuration, the study `name` specified here
+> must still match the name specified in the server-side configuration; this is
+> used to implement sanity-checks on the server.
 
 ### Study Configurations
 
@@ -80,14 +80,14 @@ for the study. The first experiment matching the active platform will be used.
 
 ### Experiments (Groups)
 Each *experiment* is a dictionary that must contain the `name` key, identifying
-the experiment group name. This name should match the FieldTrial experiment
+the experiment group name. This name **must** match the FieldTrial experiment
 group name used in the Chromium client code.
 
 > Note: Many newer studies do not use experiment names in the client code at
 > all, and rely on the [Feature List API][FeatureListAPI] instead. Nonetheless,
 > if a study has a server-side configuration, the experiment `name` specified
-> here should match the name specified in the server-side configuration; this is
-> used to implement sanity-checks on the server.
+> here must still match the name specified in the server-side configuration;
+> this is used to implement sanity-checks on the server.
 
 The remaining keys, `params`, `enable_features`, and `disable_features` are
 optional.

testing/variations/fieldtrial_testing_config.json

@@ -3274,7 +3274,7 @@
             ]
         }
     ],
-    "InterestFeedContentSuggestionsFeedUI": [
+    "InterestFeedContentSuggestions": [
         {
             "platforms": [
                 "android"